They date to the 1940s and are from Spain. They are puuurrrfect (but expensive)- and measure about 5cm across. Pop on over to my blog if you'd like to see what I'm using them for!
Also - if you live in Melbourne, Australia, the shop that I got them from, ButtonMania, are having a huge sale soon. The details are:
ButtonMania Sale, Mon 21st June to Sat 26 June, Level 2, 37 Swanston St Melbourne.