What Blue Stocking says. That four star wheel
on the right side, next to the chain, tightens and loosens the cone clutch. It may be stuck shut after years of no servicing. Lots of Liquid Wrench, tapping with a plastic mallet, and patience will eventually free it. I also see a pawl which can be swung over and engage the chain wheel to stop it.
Dont give up on it. Those old yacht windlasses, especially one as rugged as yours, are scarcer than hens teeth. Mine is similar, 36 years old, and I wont give it up.
Like Cabo Sailor says, only someone much older than he might remember these. I took the lines for the Mayflower when the Pilgrims sailed into Plymouth.....