Sweden. Facit 137cx used, 1920 Air Mail Surcharge 20 öre / 2 öre yellow-orange inverted wmk lines in very fine strip of four (strengthened). Cancelled GNESTA 28.1.1922. Allegedly the largest recorded unit of this rare variety. Signature by H.W. and certificate by HOW 3, 5, 3 (1986). SEK 68000