The address gives us a clue as to the "when." According to RC Harvey's Meanwhile, the Caniffs moved to 360 E 72nd Street in the Upper East Side of Manhattan in 1964. They lived on the 12th floor, with his studio on the 19th (room C-1902). The building was brand new when they moved in. There they lived until 1970, when they moved to Palm Springs.
So that narrows down the date. As for what and where, could some of you sharp-eyed Caniffites lend a hand?