My current guess would be that the driving mechanism might have only had one driving tooth rather than a ratchet wheel. A pawl probably was pivoted in that slot on the wheel. There was perhaps a fulcrum somewhere along the length of the pawl, so when its pivot was moved from one end of that slot to the other, that lowered its opposite end down so it hit the driving tooth and made it rotate. If that is approximately how it worked, that projecting tooth is on a wheel that rotates and drives the gear train that drives the reel. Can you find out whether that projecting tooth is actually on a rotating wheel? If it is, there will be a sizable gear on the same axle as that wheel, inside the housing, driving a pinion on the end of the reel shaft.
