If you use Swiss-made Weinmann Vainquer/999 center pull brakes with the pivots riveted to the mounting bridge, please be careful to check for cracks frequently. The later Weinmanns with the pivots bolted to the mounting bridge do not seem to have this problem. I've had both sides crack on one rear brake, and one side on another. I refer only to the brakes with the pivots riveted to the mounting bridge. Mine were both, as far as I can tell, mid-60s or earlier. They were late enough (?) to have separate springs for the two sides.
My bikes are all riders, and I will have to sacrifice a smidge of authenticity to get the safety of the slightly later bolted design. I'll keep the cracked originals in case some future buyer (from my estate, such as it might be) can have the original parts, too.
If this causes confusion, I'll try to do .jpgs for anyone who has doubts; Dale may want to post a picture, too.
Good luck!
harvey sachs
mcLean va