Shared with you
Anachronisms
As the camera panned the drawing room, a motion sensor (or glass break detector) is in the corner of the room. Even with modern retrofitting, alarm systems were not available in 1912.
When some of the servants go to the fair and see Mrs. Hughes with her date one of them speculate that he was her brother, but Thomas tells them that all she has is a sister. However it is later established she never told anyone about her sister because she was born with special needs. She never told Carson who she had known and liked for 30 years so she would not have told Thomas whom she could not stand.
When Matthew and Mary are talking about him going up to the house to visit her father later in the day it is dusk and starting to get dark. Later when Mary tells Robert about Matthew coming to visit it is very light out.
Part way through the episode a maid (Anna) is sent to bed sick, and the cook says she will send up a Beechams Powder. Whist the Beechams company did exist in this period, Beechams Powder wasn't sold until 1926, several years after this episode is set.
The reason for Gwen and Sybil's delay in returning from a job interview is that the horse pulling the trap had thrown a shoe, forcing the girls to walk. The horse appears fully shod with shoes visible on all four hooves as it is being walked to a blacksmith.
When Anna gets a cold, Mrs. Hughes orders her to go to bed and says she'll bring her up a Beecham's Powder. While Beecham was an old and established pharmaceutical brand at the time, the product Beecham's Powder was not introduced until 1926.
As the camera panned the drawing room, a motion sensor (or glass break detector) is in the corner of the room. Even with modern retrofitting, alarm systems were not available in 1912.
When discussing the improvements to the cottages, Lord Grantham mentions the agent, Crips. In season 3, when Matthew clashes with the agent, Jarvis, we learn that Jarvis has been the agent since the time that Lord Gratham's father was running the estate.