I have a Thor 6" Auto Power.
It is silver, has a nice shape, and ball bearings.
It has UL and CSA "approvals" on it, so it probably isn't real old.
I'd guess it in the 60s era. I bought it at a garage sale years ago.
It is a nice grinder. I put green silicon carbide wheels on it when i bought it. I now have one norton blue wheel that simply kicks butt. The other wheel is still a green one.