I found another set, this time a bit shorter, with some sort of "P" logo, advertised as "performance catalog brand". This gets more and more confusing:
I found another pair, bought off of eBay from a seller in Poland. These are silver, with a blue Wheeler logo. These are quickly becoming one of my favorite obscure items. I just love this clamp! I need spare parts for when I bash up the black ones on my Trek 990.