I've recently become obsessive about playing records at the proper speed. I have the rpms for many singers, i.e. Caruso, Hempel, McCormack, Patti, Tamagno, Ruffo. I can, with the score, sometimes get it right with a pitch pipe. A couple of distiguished collectors have told me 75.00 rpm on the record...

Ebay has been fanastic to me. Depending on what you're looking for, there are a couple of great auctioners:
Larry Holdridge Records, Naucks, and Norbeck,Peters,and Ford. These are pimarily for classical and Opera.