PL.176 IMPERF (SG8) USED ON COVER. 1855 mourning envelope used locally in London with a fine 1d imperf pl.176 (SG8) lettered FF with four close to good margins tied neat London/73 duplex OC 17 55. Plate 176 very rare imperf. Brandon Cert.38595, sold subject to RPS, BPA or similar Cert. Cats. £2900 off cover. (Ref 89533).