A Penny Red with a black cancellation mark on it
The Penny Red was a postage stamp issued in 1841 to replace the Penny Black. It was the main type of postage stamp in the United Kingdom until 1879. The design was hardly changed at all.
The colour was changed from black to red because it was hard to see the red cancellation mark on the Penny Black. It was easier to see a black cancelling on a Penny Red. It is not a very rare stamp.