This is King
George V Edward VII envelope cut-out (cut square) from an envelope issued in 1904 in 1905. This die was issued on four types of envelope. Collect British Postal Stationery lists the complete envelopes starting at £2.00 used so I'm afraid again there's not much value in this cut-out, say 10p or 20p at most.
Edit: Sorry - the dangers of "cut and paste"!.