Sorry - legitimate story. Not a candidate for Snopes.com
Sorry, but it seems a bit contrived. Who were the SS agents that contacted them demanding surrender of the bills? Surely they got their names. A search of the Dallas news showed a crack down on counterfeiting, but no mention of this. I suspect that someone may have contacted them about someone trying to cash in on the bill, and they used it to sell more of them (get them while you can, because the SS is gonna seize them). I am not swayed by the one-sided reporting.