Elizabeth tells Jack that he is "way off-base". The phrase off-base originated in 1935-1940 in reference to being outside the perimeters of a military base. That phrase would not have been used in the time the show is set.
10 minutes into the episode, The main character is writing the word "Valley" on the chalk board. She makes a mistake on writing the letter "y" seconds later the mistake has been fixed and it is obvious due to the lack of curve in the added part, that someone has added it.