In the middle of the movie, Jack Webb is wearing dress Alpha uniform with 4 service stripes (hash marks), which indicates more than 16 but less than 20 years of service. Near the end of the movie, he is in his blues with 3 hash marks, indicating between over 12 but less than 16 years of service.
Movie opens with wrongly punctuated close-up of a Marine plaque with the phrase "Let's be damned sure that no man's ghost will ever say - "If your training program had only done it's job." Correct punctuation is "its".
After the Captain signs Pvt. Owens general discharge paper and as they leave the office to go meet Owens Mother, they zoom in on the paper and the top two corners are very ruffled. Once they return and the Captain picks the discharge paper back up and the camera zooms in, the top two corners are in perfect condition.
The credits at both the beginning and the end of the movie refer to Marines wearing five chevrons as "T/SGT" (Technical Sergeant). However, the Marine Corps discontinued that rank after World War II. At the time this film was made, the correct title for that rank was Gunnery Sergeant.
During a bar scene, Gunnery Sergeant Moore is antagonized by another D.I. named Joey, who wears only the ribbon for the National Defense Service Medal. Since Joey is obviously old enough to have previously served in both World War II and the Korean War, he should also have been wearing service ribbons denoting service during those conflicts.