I'm a little late to the party, but that drum really looks like an early to mid (maybe even late) 60s 1/2 ton pickup drum. 11" x 2 1/2" were the heavy duty brakes. A 3/4 or 1 ton 50s drum would have been 6 lug, and a 3/4 or 1 ton 60s drum would have been 8 lug.

Might make the search for parts a little easier. Gene