When the Ricardos moved into the new apartment, its number was 3B. Over the course of some episodes it was changed to 3D, to fit with Lucy's claim that she's been in (3-D) movies, in Lucy Tells the Truth (1953).
At the very end, as Ricky finishes explaining that he and Mr Benson had arranged for their apartments' furniture to be switched--meaning all their hard work had been for nothing--Fred and Ethel join Lucy in making her trademark "uh-ugh" face, with lips curled and teeth showing.
The magazine on the Ricardos' coffee table is the May 1953 issue of "Woman's Home Companion", which featured an interview with Lucille Ball and Desi Arnaz about the recent birth of their son Desi Arnaz Jr.. Lucy was previously seen reading the same issue in Lucy Hires a Maid (1953).