It is established by a calendar on the wall that if this episode is set in the 50s, it could only be the actual year 1950. But the song "Yakety Yak," which features prominently in the episode, was not released until 1958. It's possible this is a sign of the show's manufactured reality.
The front door handle set is installed backwards. The exterior side of the door has what should be the interior knob with bottom screw cap and the interior side of the door has the thumb latch handle that should be on the outside.
There is no year on the calendar in the kitchen.