Saving Old Seagulls

Does anyone know how the handles on the stainless steel transom screws are meant to be held in place in the slot in the end of the screw?

One has fallen out and it looks like there might have been solder or something similkar holding it in....

The other one is loose, so I'd like to fix them properly. What's the best procedure?

Post a picture Mark all the ones I've seen here are a very tight fit in the slot & have a pin / rivett through them.