Looks like a portable manual grinder. A grinding wheel goes between the washers on the bolt and it can be clamped on a bench or other horizontal surface with a lip.
i have one just like that it is a sharpening tool for axes shears knives if big enough it will bolt on to a table and away you go it is a mini version of some of the big wheel versions used for same purpose not sure whre to access the sharpening wheels might google whetstone 'not sure of spelling' im sure they are still ou there good luck
1993 NH 2120 (the best), 1974 MF 135 (sold, but solid), 1947 Farmall A (bought, sold, bought back, sold again), 1956 MH50 lbt (sold, in 1980, darn it)
+2 on hand-cranked grinder. They're a real pain unless you have a compliant helper, since you almost always need more than one hand to position the blade. Kinda cool, but not so useful.
Jim