These are Evinrude and Johnson antique outboard motor piston rings. They will fit all the 10hp OMC outboards made from 1956 to 1965 and probably earlier. OMC part number is # 378416 or 0378416.  That number is for a set of three.  We have 17 of these rings. We sell them each.  If you need only one ring you don't have to buy a set.  2 3/8ths by 3/32nds.  Black iron.  Pin cut ends.  Look at the photos and email with questions.  Thanks for looking.