I got a few of these directly from the post office at my clubs stamp show.
Covers from the dedication of the Doug Flutie statue. Silk Cachet, and a BC eagles logo stamp made by Stamps.com. These were excess that didn't get cancelled at the event. They're unsealed, and the stamps are valid anytime, so you could mail them.
But I think they'd be better for autographs or some sort of display.
I got a few, $3 each shipped, Most any sort of payment ok.
Steve B