Hard to tell but may be a .32 rimfire for the likes of hte old Stevens Favorite or 1893 Marlin - came in both .32 Short and .32 Long - that was standard - there were others like .32 extra Long etc.
There was also a .30 Rimfire but it would not be one of them as they are like hens teeth.
Going by the size of it compared with a .22 it is hardly likely to be a .25 Stevens short, long or extra long.
It could also be faintly possible for it to be a .32 Centre fire Smith and Wesson projectile.
Always great trying a new beach first target musket ball then spent half an hour pulling my daughter out of the mud… 1876 penny is completely rotted but date still readable 42 sixpence in good nick I think the decritive thing might be for a scarf as for the whiskey top looks old