Not a hoax, Bart. It is shown in both the 1980 and 1993 editions of the Dickey-&-George books. Emike's specimen in missing the lead band sabot which encircled the top of the shell's conical "tail-section" above the fins. A small flange at the top of each fin locked the band-sabot in place, to impart the spin from the cannon's rifling.
Regards,
Pete