Hi all, just picked this up the other day. I thought it was interesting, with an unusual history. https://en.wikipedia.org/wiki/Bernard_von_NotHaus
Interesting -- it's kind of like a gift certificate for a 1/4 oz. of gold, except it will expire in 2027 if not used. Looks like you have to combine the certificates to redeem for a full ounce (or purchase with cash). Probably best to wait until silver tops $20/oz. again, right now you'd lose a few buck to redeem it. Neat item! Edit: I just read the wikipedia story -- looks like you won't be cashing that one anytime soon!
They were "warehouse receipts", borrowing a term from the Uniform Commercial Code which is often cited by anti-government groups. They were originally issued using a base unit of $10.00/oz. for silver. When silver went over that amount the base unit became $20.00/oz. I am not sure how many of the supporters saw the irony of having to re-value their "currency" in a way that it lost half its value.