My thought was that it was for grinding down some part or tool. At 1/2HP, it isn't really a big unit. Perhaps it was for grinding mower blades or had a angle jig that fit on the bed and was for sharpening drill bits. Montgomery Wards made a lot of shop tools, but that one isn't familiar to me.
If I only get one guess, I'd go with drill bit sharpener. Look around and see if there is a funny looking thing that adjusts to angles and has a "V" shape rest. It would slide onto the bed ad be held down by those two bolts.