
Penny Black!, nice Stamps!. Really It was issued in Britain on 1 May 1840, for official use from 6 May of that year.
Although 6 May was the official date that the labels became available, there are covers postmarked 2 May, due to postmasters selling the stamps from 1 May. A single example is known on cover dated 1 May 1840.
Here is the Cover of May 1.
http://documents.davidfeldman.com/u...6_99_FEB.pdfRegards!
Rodolfo