Radio transmitting devices in the early 1980s would have used large batteries to transmit for lengthy periods of time and due to the batteries not holding a charge. Such a device would have been noticeable inside of the briefcase as it would have been at least the size of a box of bank checks or larger.
Smaller transmitters only became possible with the widespread introduction of cellular technology from the mid-1990s and forward. It would not have been available in the film's 1980s setting.
The $100 bills in the satchel have the signature of Treasury secretary Nicholas Brady. $100 bills with his signature were not printed until 1989. The newest possible $100 bills circulating in 1980 would be Series 1977 bearing the signature of secretary Werner Blumenthal.
When Bell responds to the hotel shooting, a modern Carl's Jr. restaurant is seen in the background over his shoulder. Furthermore, Carl's Jr. was not operating in El Paso in 1980. In addition, when he is driving to the motel, as he first hears the shots, a modern day Wendy's sign is seen behind him.
The opening scene of the police car features a 1990 Chevrolet Caprice and not a 1980 (or earlier). This is evident from the front door mounted seat belt mechanism, which was only used on the 1990 square-body models before the car was totally redesigned in 1991. There are also numerous mid-late 80's Caprices in the film - all too new for the setting of 1980. These cars are easily identifiable by taillight and grille design to differentiate them from a 1980-84ish car.
When Carson Wells is trying to talk Anton out of killing him, he offers to go to "an ATM" to withdraw $14,000. Although ATMs were invented in 1969, they were not in widespread deployment until banking deregulation in 1984. The small Texas town they were in would not have had an ATM and, even if it did, it would not dispense $14,000.
During his encounter with the gas station attendant, Anton pulls out what he says is a 1958 quarter for use in a flip. A quarter with this date would have been made of silver, as opposed to the copper-nickel sandwich coins in use in the United States since 1965. The U.S. stopped minting silver coins in 1964, so it is unlikely that Anton or anyone else in 1980 would have had a 1958 quarter in pocket change -- almost all the silver coins had been hoarded or otherwise removed from circulation by the late 1960s.
The film takes place in 1980, but the Dodge Ramcharger driven by Anton in part of the film is a mid-'80s model. From its introduction in 1975 until late 1980, the Ramcharger had a removable hard top and chrome grille. Starting in 1981 the Ramcharger had a plastic grille and the top was welded to the body and was not able to be removed.
In the scene where Llewelyn calls Carla Jean from a rotary bank of GTE pay-phones, there is a clearly visible graffiti tag above the phone in silver ink. Not only would this kind of graffiti be hugely unlikely in Texas in 1980, but the tag is dated "06".
The weapon Moss picks up in the drug dealers truck is a Heckler and Koch SP89, so named because it was introduced to the American market in 1989. It was also a unique variation and was not sold in that form outside the US but modified specifically to conform with US gun laws.
The $100 bills in the satchel have the same serial number of L14439604A. The bills appear to be from the the 1977 series, however has the wrong signature of Treasury secretary Nicholas Brady, which did not appear on the US notes until 1989. Based on the serial number the banknotes were printed in July 1979 at the San Francisco Federal Reserve Bank.
In the shoot-out aftermath scene, the red Ford Bronco has a FORD blue oval emblem/logo on the grill, as well as F O R D lettering on the leading edge of the hood. While the hood lettering was used on 1980-1982 models, 1983-1986 models used the updated grille insert with the blue oval. This grill would have not been available in 1980, either the truck's grill or the hood has been changed from original.
Although day trading started in 1971, NASD created the Small-Order Execution System around 1985 to enable people to become day traders in the sense that we know it now, but it's unlikely the term would be used in 1980 by Carson Wells as it would today.
When Sheriff Bell is going to find Moss, just before the Mexican's pickup pulls out ahead of him, there is a sign for a Vietnamese grill on the right side. Since the majority of Vietnamese immigrants did not arrive until after 1980 it seems unlikely that this restaurant would exist.
When the American border guard asks Llewelyn what outfit he was in Vietnam, the answer is "12th Infantry Battalion." This answer wouldn't make any sense to anyone familiar with how the army is organized and in fact would indicate that Llewelyn had never been in the army. (Every infantry regiment has ad-hoc numbered battalions. No regiment has as many as 12.) An infantry soldier would identify his unit by company and regiment, or just by regiment.
When Anton enters the Texaco Station and asks the owner behind the counter how much the peanuts cost, the owner replies "69 Cents". As he says this, immediately to his right, viewer's left, there is a clip strip of the same peanuts all labeled 99 cents each. (We can tell it is the same kind of peanuts as Anton later discards his wrapper on the counter.)
When Bell enters the El Paso motel he draws his 45 auto and thumb cocks the hammer. No experienced lawman would ever carry this kind of pistol in the half-cock position. He would carry the gun at full cock with the positive safety engaged.
Chigurh hurt his wrists badly from handcuffs in the beginning of the film. Yet for the rest of the film - the story takes place in the span of a few days - his wrists don't show any marks or scars whatsoever, even in the close-up shots.
When Chigurh kills the two men who gave him the transponder the taller one is on the left and the fatter one on the right. They both fall backwards. When Bell sees the bodies the next morning the taller man is on the right.
When in room 138, Moss slides the suitcase to the left of the HVAC duct, handle-side first. When he retrieves the case from room 38 (the room directly opposite) by hooking into the handle the case is on the wrong side of the duct for the handle to be accessible.
A license plate is used on two different cars. In the scene about 1hr 3min just after he crashes the pickup truck, when Anton is walking up to the pickup, the car immediately behind the smashed one has a Texas license plate 350 R2H. At the end of the movie Anton drives away from Carla's house and the Olds he is driving has that same 350 R2H Texas plate.
When Sheriff Bell turns on his siren to pull over the flatbed truck with the recovered bodies loaded on it, the highway has a very narrow shoulder, less than half the width of the truck. When the truck actually pulls over, the shoulder is very wide - nearly twice the width of the truck.
When Sheriff Bell is driving up to the motel as the Mexicans drive away, his seat belt holder is clearly attached to the B pillar on the car. When Bell gets out of the vehicle at the motel, the seat belt holder is now attached to the upper part of the door itself.
When Sheriff Bell returns to the Desert Sands motel, we see his shadow squarely approaching the motel room door, as if he's walking directly towards it and the car is directly behind him, but in the next shot, he's just passing in front of the left headlight of his car.
When Anton drives his car and two boys ride their bikes and chatter behind him. When we see them through the back window of his car, they're passing a beige pick-up truck and are somewhere in the middle of the street. In the next shot, showing them in the back view mirror, they appear to be on the left side of the road and passing a red car. The pickup truck is nowhere to be seen.
When Moss picks a cab to take in Del Rio after exiting the airport, behind that cab is a cab with a license plate of J8R-725. Later in the film, at the crime scene, Moss's wife drives up to the motel in a cab with the same license plate number, J8R-725, as the one outside of the airport.
In the scene where Moss is talking to the lady outside in the pool area you can see a newer model of a Chevy or GMC Tahoe (01-06) in the parking lot of the Carl's Jr. It then disappears and re-appears twice.
After Chigurh blows the lock to the hotel room with the Mexican reaching for his gun, the phone on the table next to him is at an angle. However, before Chigurh shoots the man's arm, the phone has shifted in a different direction.
When Moss returns across the bridge from Mexico back to Eagle Pass, he has no clothes. He returns to the Western store where he bought his boots, but the plot established that the store was in Del Rio, over 55 miles away. Then he is in his new clothes by the river in Eagle Pass retrieving the satchel of money. Did he travel 110 miles to buy clothes?
The sign that shows that Anton is driving towards Del Rio is incorrect. There is an arrow that shows Highway 90 veering off towards the left and Del Rio veering off in the opposite direction of the fork in the road to the right. In fact, the only highway that comes in and out of Del Rio is Highway 90. If Anton was driving to Del Rio, he would be on Highway 90 heading towards Del Rio.
When the Mexicans flee the Desert Sands Motel in El Paso, a Bank of the West tower can be seen in the distance. El Paso has no such building. That building is located in Albuquerque, New Mexico, where the scene was filmed.
The cattle gun used to blow the cylinder out of the center of the lock is not possible as shown in the movie. If the center of the lock was blown out, the bolt that secures the door to the frame (the large steel piece that slides out of a lock when you turn the key on a deadbolt) would still remain in place, and would still remain securing the door to the frame. Simply blowing the cylinder out would not be sufficient for quick or easy entry it would simply eliminate the need for a key. One would have to be able to fit a tool or their finger into the hole that was created and somehow pull the bolt back into the door, or possibly have to rotate the entire mechanism inside of the lock housing, as you would with the rotation of a key - and therefore ruining the element of surprise.
The physics of Chigurh's punching the locks out with a compressed air rod, while being quite captivating and fascinating, are impossible. In order for this method of entry to succeed, either one of two physical factors must be involved: (1) either the deadbolt, which traverses the interior of the door, must already be cracked or broken in the middle, or (2) the opposing force must be equal or greater than the original force. In the second case, Chigurh is seen holding the punch rod to the door lock and not suffering any kickback. Chigurh would have to physically hold the air rod so firmly that the counterforce of the rod hitting the lock would actually work and blow the lock out. In reality, the air rod hitting the lock would create such a counterforce that Chigurh's hand would be instantaneously pushed back, because a traverse deadbolt could not be punched out as depicted.
In the shootout scene at the Eagle Hotel, you would think Anton would use the semiautomatic shotgun, as he did in the shootout at the motel in Del Rio. Indeed the window shot at the Eagle Hotel shows him aiming his shotgun. However, all the gunshots are in fact bullets, and after the truck is wrecked, they show Anton had dropped an automatic handgun.
The sheriff mentions that his father was a "sheriff" up in Plano. This is an error for two reasons:
1) Plano is not the county seat in either of the two counties where it is located - The sheriff's office is always located in the county seat of a county and Plano isn't one.
2) Until the mid-1980s Plano was a tiny city in the distant Dallas suburbs. While it is medium-sized city now (270k population), in the 1980 setting of the film, the population in Plano should have been roughly 20,000 people and was very peaceful. It's possible that someone who wasn't familiar with the Dallas Metro area might not have even heard of Plano. Being a "sheriff" there then would have minor role if that role even existed.
When Llewellyn first checks into the Del Rio Regal Motel, he has a conversation with the front desk woman that ends with " i'm just one person so it doesn't matter the size of the bed." The room he is assigned is room 138 and it has two beds in it. Later when Llewelyn returns and inquires about renting another room he selects the room right across, room 38, and the same woman says "it's got two double beds" inferring that why would he need a room with two double beds but he actually already has one.
When Llewelyn finds the radio transponder in the briefcase containing the money, the stack the transceiver is in is actually a stack of $1 bills with a $100 bill on the top. Which is understandable because a typical stack of one-hundred dollar bills amounts to ten thousand dollars. Why destroy that much cash when one could achieve the same effect (hiding the transponder) by defacing far less currency?
It is true that mobile home doors are sealed in a way that would prevent mail from being slipped under the door. However, all doors for older mobile homes were also made to swing outwards to open, never inwards. The door in this movie swings inwards. It is obvious that the set-makers modified this home, especially for the dramatic effect when the door swings open to reveal Chigurh standing there. But, who is to say that somebody hasn't replaced the door in the past so that it opens inwards now?
A radio transmitter like the one shown as being secreted in the money briefcase would have had, at best, a range of a few miles. Without an aircraft to track it and without a more than general knowledge of its location, it would have taken Anton Chirguh days or even weeks to locate its signal. And given the transmitter's limited battery life, it would have stopped transmitting well before he was able to do so.
Llewellyn simply leaving the area where he found the money should have been more than enough for him to have disappeared and probably never be found.
Moss takes great pains to ensure the concealment of the money before he knew there was a transponder inside it. He is shown doing this by hiding the case inside a ventilation shaft at the Motel in Del Rio and pushing it as far back as possible with the closet rod, and then all the way to the left. Later, Moss gets another room opposite the one he was in--room 38 is behind room 138--and pulls the case from the wrong side. If he was in fact pulling the case from the right side from the second room as shown, the two rooms would have been only the width of the case apart. As it is, the ventilation shaft is in the center of the motel rooms, so since Moss originally had put the case on the far left of the ventilation shaft to the first room, then he would have only been able to grab it from the left side, not the right side, in the second room which was on the opposite side of the building.
Moss had Chigurh dead to rights when Chigurh found him at the second motel (room 213). After Chigurh blew the lock out at Moss, Moss fired one shot from his shotgun, slung arms and then threw the money out the window where he jumped. Why didn't Moss just stay where he was and ensure that Chigurh was dead? Why did he give Chigurh another chance to kill him, when Moss had several shots remaining pointed right at the door?
When the Mexican in the motel bathroom is shot the shot passes through the wall, which should hit his left hand, but hits him in the chest. As he falls his gun is firing at the bathroom door, but leaves no holes.
When Anton is entering Llewelyn Moss's trailer, he picks up his mail, however there is no mail slot in the door and trailer doors are manufactured with rubber weather stripping, preventing air (or mail) from being slipped under.
When Sheriff Bell pulls over the flat bed truck carrying the bodies of the dead Mexican cartel members the driver states they only took the truck instead of a van because "We didn't have a van with four wheel drive." However at the time the driver states this you can see the lower control arm on the front suspension of the truck he is driving. This is a characteristic of a Chevrolet truck of that era that is two wheel drive. A four wheel drive truck would have a leaf spring straight front axle suspension.
The goof items below may give away important plot points.
After Anton blows up the car outside the pharmacy, numerous car alarms and horns sound off. All those cars didn't have horn alarms, and loud ringing car alarms weren't prevalent until the mid 80s, but would have been very rare (non existent) in Eagle Pass in 1980.
When in the beginning of the movie Anton Chigurh is arrested, he walks to the car with his hands behind his back. The chain of the cuffs counts 3 links. When he strangles the deputy, the chain of the cuffs is much longer, like 7 or 8 links. When he puts the cuffs in the sink, there are again 3 links in the chain.
When Anton shoots the two men after being handed the detector, the tall, young man is on the left and the older man on the right. But when the sheriff is surveying the scene with the other officer and come across the killed men, they have switched sides with the older man on the left and the younger man on the right.
Anton's car changes direction between 2 shots when it gets hit in the car crash at the end of the movie. In the interior shot of Anton, the front of the car moves to the left during the crash (seen from the driver's point of view). In the following long shot the front of his car moves to the right, inconsistent with the interior shot.
After Anton shoots Carson, he turns towards the bed as he picks up the phone and answers the call from Llewelyn. As he speaks, blood from Carson flows straight towards the toes of his boots, but Carson was to his left at this point and his boots were facing the bed. Carson's blood would have had to flow towards the bed, then turned right about 135 degrees in order to flow towards Anton's boots.
Llewelyn throws the money bag over the fence on the USA side of the border station just before walking past the border guard. When Carson Wells spots the bag through the fence he is on the Mexican side, there is a sign visible that says "Enter the USA" above the door, indicating he is in Mexico.
When Anton lights the gas tank of the car on fire that is in front of the pharmacy, the interior of the car explodes and blows the windows out of the car before the gas tank explodes. The interior would have been the last thing to burn and would have most likely never exploded.
How, exactly, did the sheriff in El Paso know that it was, in fact, Chigurh who came back to the Eagle Hotel to kill Carson Wells the next day, and how would Ed Tom know the same to tell the sheriff? There were no witnesses, either to the killing of the desk clerk or of Carson Wells, so how would either sheriff know "to a certainty" that the killer was Chigurh, especially when Ed Tom referred to Chigurh as a "ghost" and didn't even know his name?