I bought a used 32 caliber flint lock on line, & it has something similar... ( doesn't look rivited on... looks glued or welded ) & uses a piece of steel in place of the flint... I think it's Ferocerium ( modern fire stater rod )
BTW... this is my 1st attempt at flint lock ( so to speak ) but it shoots awesome... in my 1st 5 shots ( while figuring out what I was doing ) the last 3 shots I could cover with a dime at 30 yards