What gun for this large centerfire?

The consensus at SLICS was that this large CF cartridge was possibly homemade based on machining marks on base and neck at crimp. Still would like to know what gun it was made for?
Dimensions .642 bullet, 1.78 cartridge length, 1.22 case length, .685 base diameter, .805 rim diameter. By the way, Mel Carpenter and Vic Engel did not look anything like what you gentlemen described before hand.

Could be a demonstration dummy (inert)
Or an early CF conversion of a muzzle loader. BULLET diameter is 16.3 mm (.642)…is that one of the shotgun gauges?? .20 ga. Maybe?
The primer looks too small for a rifle breech loader. ( .USUALLY
.250 or more)
Further resesrch tells me very close to .20gauge…light ball load, probably blackpowder.

Back-up in case one encounters a Boar in the woods?

Any other suggestions?
Doc AV.

Thanks Doc. Hopefully some others can shed more light

It is close to a 2X 32 S&W.

Maybe pulling my leg? 2X32 equals .64 caliber but not sure how you would fire it and find no info that gun.

There is a possibility that someone tryed to diddle with a 57Snider but even for that the
base is to big ,the Snider base is about 660-61 this one is 685.Their is nothing that would
even come close (In CASE MEASUREMENTS)

French Tabatiere round?