I think it is a bit older than you think it is. It is essentially a honkin big die grinder, used for cleaning castings, welds, heavy steel. They havn't made them like that in a long long time, they were very dangerous. look at the speed that thing rotates at, now imagine accidently dropping it, and the wheel exploding at that speed....
I have catalog info for Thor, who made one similar , circa 40's. Unfortunatly, early Skil info seems hard to find in general.