They are, or were, 'bullet' shaped and 'grease grooved' lead and then fired at a hard target. The barrel does not seem to be rifled with more than 3 grooves and shallow ones at that. They deformed - mushroomed - on contact. Measurements needed for caliber and (maybe) weight. They look small - .31" - which was about the smallest used at this time for a pocket revolver.
Lines or scratches - which also may be the remains of the effect of rifling. Attached is an old diagram of an Adams .44 revolver bullet (in the square). Look familiar? Same effect for any lead bullet striking a hard target.