So what did it come off of?

My dad has had a pair of these lights hanging in his barn for as long as I can remember. Some people who have seen them say 29 Caddilac or early Buick but I would like to know for sure. I did a few searches over the years and came up with nothing solid. Please forgive the crummy cell phone pic.

 

1928 or so Buick ( i have a pair up in the attic ) and an old German plate.

 

I was thinking Buick I guess I need to dig a bit more.