I just purchased a 936 that is missing the mainspring barrel (naturally the arbor and spring too). As I look at swigart's it appears the same msprg barrel was used for lots of different grades. This particular 936 has a 4 digit serial number so it is a very early production. I don't actually have the watch yet, but will either need to purchase a barrel and arbor, or take one from another movement. Any help will be appreciated.

Mike,
I believe any 18s Hamilton m/s barrel and arbor will fit, as long as it's not a motor barrel.

Thanks Brian. That was what I got from the book but sometimes you just like to be sure.