Gibraltar 1836 cover to London 1/2d handstamp in Green

1836 (28 July) entire letter to Edinburgh headed H.M. Ship Asia at Sea and written by Thomas Cochran on approach to Gibraltar (transcript included) showing on reverse very fine GIBRALTAR / F (without date) H/S of Falmouth in bright green with red AUG 31 1836 cds below. Rated 3/1 on face with framed additional 1/2 in green alongside. Very fine and rare. (N.B. The GIBRALTAR / F H/S was used at Falmouth to identify incoming packet mail from Gibraltar in order to evaluate the cost to destination.)