It appears to be a "Segregator". Shovel raw dirt/sand/gravel into the hopper and as it turns and the material flows through from gravity the dirt* if any, fine sand, coarse sand, small gravel, larger gravel, and finally whatever is too large to fall through the graduated screens falls out the end.
Hopefully if they were sorting "bank run" sand/gravel it would have been washed first to remove whatever dirt was in the mix so only clean sand and gravel would be handled.
Interesting how the drive has a chain wheel, a flat pulley so it could be driven from the PTO of a tractor or pony engine, and a hand crank! I can't imagine turning that thing by hand. But if you look very closely you can see the drum is gear driven, and would have a very high gear ratio so the crank might not be that bad.
I would guess it is pre WWII, most likely the nineteen-teens or twenties.