Like a DA, I left a pound or so of fert in my solo chest spreader over the winter. I checked everything out before I started my first app this year and you guessed it....it wouldn't crank. I took the base portion apart and now I am very familiar with the inner workings of it. The gears are metal but not stainless and are lightly greased. Very sturdy and sealed as best as can be expected. It's one weakness is where the spindle comes down and joins in the gear box. The spindle is mild steel and has a grommet it spins within much like where the spindle goes through a push spreader hopper. It was rusty and would not spin within the grommet so I used some spray catalyst and was finally able to remove the spindle from the grommet. I used fine sandpaper on the spindle and slopped it up with never sieze and put it all back together. Works like a charm. It's a great spreader overall. IMO, to have something of professional quality something of similar design would have to be done and the one thing I would change about the Solo would be to have a stainless spindle and I think the same would be necessary in any quality hand spreader.
"The Poor Fish" circa 1930's: The Poor Fish wouldn't have been caught if he'd known enough to keep his fool mouth shut.