In your pic the 2:00 position looks like a countersunk hole, that is where one of the "two bolts", really screws, would have been. If you don't have any then the drum is ready to come off.
May need to back the brake adjuster off and use some penetrating oil on the hub/studs. Sometimes it can be difficult if it's rusted in place.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-