When Harry goes to tear up the IOU, Lucy warns him that it will do no good because it's a photostat. The document Harry is reading, however, is on yellowed parchment paper. The paper has a small black mark in the same place as the document Lucy pulled out of the diary in the attic in the previous scene.
When Harry opens the door of the closet, there is a wall calendar that reads JAN. The year appears to be blacked out, but since the first of the month falls on a Sunday, it is likely from 1967 or (less likely) 1961. The episode was filmed in 1969 and aired in 1970.
The framed painting of Harry's great grandfather hanging over the fireplace is actually a doctored black and white photo of Gale Gordon that hung over Mr. Mooney's mantle on "The Lucy Show."
Harry's home and living room are differently configured than in previous episodes.