10's and 11's are a very noticeable diameter difference. Any old 10 or 11" drum will confirm what you have. The flange measurement Robert talks about will confirm the shoe width. It might not hurt to have and old housing and axle laying around to double check the b/p fit with the drum...
I've got a couple laying around I can double check if you find out what you have and maybe need a application to order everything else for...