I have no idea where you’d get one of these but if anyone out there in the interwebs finds out, please email me immediately.
The video poster, GunOwnerDan, had this information on the totally awesome and unbelievably bad-ass Brass Knuckle Knife Gun:
Called the “French Apache” or “Apache Knuckleduster”, these were made in Belgium by Lambert Dolne in the 1870’s and are considered to be one of the most unique pocket pistols ever made.
This one fires 7mm pinfire cartridges which went out of style in the late 1800’s.
Other calibers were also made including some that could shoot rimfire cartridges. It’s double action and can fire 6 shots as fast as you can pull the trigger.