I just replaced the windlass motor/gearbox on our boat and there is a clip on the windlass shaft that holds the 1/4 bronze key from slipping out of the assembly once it is all together. I had that same shaft here at the house earlier this week for a little rust removal polish session and now it is happily installed back on the boat. Yesterday I was walking to my truck and I saw a little clip on the driveway..... Now I've got to remove the motor just to see that I didn't leave it out. I'm certain it is there but I can not imagine what else this clip could be. It doesn't have to be a cotter pin!
BB