Midge falls off a stage in the previous episode and is found wearing a sling at the beginning of this episode, but her arm is out of the sling and working fine during her stand-up act about halfway through the show.
Midge talks about winning a Salad Spinner, a product that wasn't patented until 1973 and wasn't sold to the public until 1974.
The matchbook for the strip club Midge works at as an MC is a reverse striker as opposed to a front striker. Reverse striker matchbooks weren't in use until the 1970s, and weren't federally mandated until 1973.