This concerns the vintage GayFreres bracelets for El Primero. According to those in my possession, ZJ endpieces go for the A 386, and ZKM for the angled tonneau cases. So what then do ZK endpieces go with? David put the question ot me, and I have no idea - they look like ZKMs to me. Moreover, I can't think of another model that requires a convex endpiece. Any ideas?
Here's David's picture of a ZK endpiece: