Gibraltar to Hong Kong by Airmail

[Frank Schofield]

Just picked up an unusual item at our local show, addressed to Lieut. L.K.H.J. Harvey RN, HMS Ceylon, c/o FMO Hong Kong, on an envelope slightly larger than the modern C5 size, endorsed in m/s "Air Mail" and franked with 9 (nine) Gibraltar 1/- stamps (perf 13) and postmarked by double ring GIBRALTAR / 30 NO / 51, on the flap is an oval cachet of Saccone & Speed, Wine, Spirit and Tobacco Merchants.
I have checked Proud's book on Gibraltar and cannot find an Airmail rate for this amount, the closest being just over 9/- for the heaviest parcel rate. The 1951 Gibraltar Directory and Guide book is no help it only quotes an airmail rate to GB other countries rates on application.
Why such an heavy rate?, the envelope could only hold a mess bill, or perhaps a Wine List, or simply philatelic.
Saccone & Speed had branches all over the world, but not Hong Kong

Frank Schofield