Great Britain 1860 Exeter to Seetapore Calcutta India Military Cover & Letter via France

Cover, with enclosure, to Lt. Colonel John Clarke, Commissoner, Seetapoe, Oude, Calcutta, franked with 6d lilac (S.G. 68) and three 1d rose red (S.G. 40), tied by neat Exeter duplex cancels (March 6), paying he 9d single 1/2oz rate, endorsed "via Marseilles" at lower left, with Whitestone double-arc despatch, London (March 7), Calcutta (April 9), Lucknow / Sorte (April 13), and Seetapore (April 14) backstamps, back flap with small "Dinna Forget" label, some trivial wrinkling, but a remarkably fresh cover to a desirable destination.