Found these at a co-operative. They were $5. They felt better than any of the other centerpulls in the bin, including the mafac racers and some shimanos.

They have a huge reach, around 70mm-100mm, so I'm thinking they're BMX? They are also stamped with the JIS logo, and have "Japan" on the inside. The straddle cables have an "A" on them. Or maybe it's a really weird "D."

I'm thinking if I ever need to convert to 650b, these will make it possible on whatever frame I choose.

Thanks for the help!