Thanks Al -
The car never had A/C, but that doesn't mean that this horn wasn't from another 113 that did have A/C. After reading your reply, I looked closer at the stamped metal (painted) bracket, and you are correct, it does show evidence of welds that have been ground off.
If I don't have A/C, and I want to return this to the original configration, do I just eliminate the (2) metal pieces that I think you refer to as the "L", and bolt the horn directly on the stamped metal bracket? Or maybe just the piece close to the horn?