According to ATF's website on the subject, to qualify for Curio & Relic status in the United States, a firearm must be at least 50 years old, be certified "of museum interest" by the curator of an officially recognized museum that exhibits firearms, or "Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event."

I submit to you that the ZiP™ 22 meets that specification in spades. It's definitely novel, rare, and bizarre, and I sincerely doubt that anyone who wants one wants it for actual being-a-gun purposes. If I had one, I would be boxing it up to send off to ATF for evaluation as we speak. (You have to send them an actual example of the gun you're proposing for inclusion. The website kindly lets you know that if it's an unregistered NFA item, i.e., one you weren't supposed to have, ATF "may be unable to return" it.)

--G.
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Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
zgryphon at that email service Google has
Ceterum censeo Carthaginem esse delendam.