There is an issue with the "wallet' guns. There were a few, notably some 2 shot derringers that would fit in a leather case that looked like a wallet, but had a hole in the side for your trigger finger.
The ATF ruled that IF the gun could be fired while still in the wallet, the combination of gun & wallet met their definition of a "disguised firearm" (think about a cane gun) and as such, the combination of gun and wallet had to be registered as a NFA class III, under the "Any Other Weapon" classification.
Yep- that's right- a piece of leather had to be registered as a Class III. Go figure.
What we have here is... failure- to communicate.