Question About Penny Black

are penny black issued in stationery
I found one heavy paper




*** Moved by Staff to a more appropriate forum. ***

No - the stationery available was the Mulready envelope. Is this stuck on other paper?

Try to identify the plate.

Could this be a reprotuction printed on a philatelic publication or similar, which someone cut out?

The South Kensington Exhibition proof would have been printed on thick white card, but should not have a Maltese Cross cancellation. It was not printed from a black plate.
This one has a cancel, that would rule out exhibition reprints, unless the Maltese Cross was forged.

I suspect it is a cut-out from some print (album, card, brochure) that reproduced a cancelled example. The nicely rounded corners hint to this.

A closer scan might show the machine turned details in the background if it's genuine but still on paper...