If Hintergnomes existed, they'd surely have some kind of guild regulating the production and sale of Hinterpockets, some kind of Hinterguild of Pocketers and Bagmakers. Thankfully, Hintergnomes don't exist, and so no such regulatory body can exist either. As a result, there would be nothing unusual or noteworthy about a hypothetical Hinterpocketer who might be selling Hinterpockets unsanctioned by the Hinterguild, as they wouldn't exist either.
