Tom,
I'm not up on the 69 rear defrosters so I'll have to bow to someone more knowledgable. However, I do have a picture of that same unit at home where the guy also said it was from a 69 Camaro Convertible. The date code on the motor is 8-68, or August, 1968. Seems to me this is pretty early for 1969, but if the ebay seller's correct, when did the change take place??? I would ask the ebay seller what the date code on his motor is.
I also have another unit that looks like nither of these supposedly from a 69 Convertible. I'm not at home right now, but I'll post pictures of all the ones I have when I get home tonight if needed.
The problem here is that this is such a rare option, very few poeple are experts and every GM car from that period had a rear defroster as an option! If you do bid, have him give you a written guarantee that this will actually FIT!! It looks to me like it won't.
Ed