Bermuda. (Gibraltar - Libya). Air Mail envelope addressed to Gibraltar bearing Bermuda SG 156, 6d black and deep mauve tied by Hamilton slogan '13 Dec 51' , underpaid with 'T/ Bermuda/ Centimes 4d' duplex in red on face and bearing Gibraltar postage dues SG D2, 2d sepia (pair) tied by Gibraltar receiver and obliterated with cork cancel and forwarded to Benghazi bearing Libya postage dues 10 mills scarlet (block of four) tied by Benghazi/ Registration receiver. Remarkable postage due cover.