[TARNATION !!!]

Came across this cap. Owner has had it stored for 30 years and got it from his grandfather. He believes the cap is original. Was there ever such a cap installed at manufacture. My thoughts are no, but as Dean says, "never say never"... I had a quick look at the Fox site. Do they have a SN lookup like we do? I can't find it if they do. The gentleman says it is a 1921 gun. SN is 930xx as best I can make out on one pic.