Great Britain 1869 Postage Due Cover Derry to HMS Peterel at Sierra Leone

Cover the Hon. Ernest Cochrane on the HMS Peterel at Sierra Leone, franked with block of four and pair perforated 1d. red (Plate 129), all tied by Derry 172 duplex (12 October), headed "Officer's Letter", carried by the Mandingo on the African Steam Ship Co. service, unframed "INSUFFICIENTLY / PREPAID" handstamp in red with manuscript "over 1/2oz" beside, red crayon "2"manuscript (2d due to Sierra Leone), "9"(9d due to UK for half the 6d fine and all of the unpaid 6d) and "1/-" (due from addressee, deficiency of 6d plus 6d fine), markings on front, backstamped Derry (Oct 12), London (Oct 13), Liverpool bag (Oct 13), Liverpool PLO (Oct 14), and Sierra Leone (Nov 6), various small faults as expected, else a scarce letter to a British naval ship in Sierra Leone.