The Barbados Post gives the following info by the vessel depict on the $ 1.15.
In 1895 after the Royal Mail Steam Packets Company (R.M.S.P. Co) transferred its operation from St Thomas to Barbados, activities in the region were intensified and larger ships like R.M.S. SOLENT and the R.M.S. ESK regularly serviced the down-islands and the Leeward Islands.
The mail was transported between Falmouth and the West Indies by means of fast sailing ships called “Packers”. These were owned by the British Government or in most cases hired from their commanders who owned and ran them. They were anchored in Carlisle Bay where the cargo was offloaded onto “lighters” – large wooden boats propelled by men with long oars.
In those days sailing the seas was a fairly risky business. Commanders of the vessels were issued with strict instructions in relation to their handling of mail: their primary duty was safeguard the mail: to outsail rather than engage the enemy and if in danger of being overpowered the mail was to be weighted and sunk.
The R.M.S. ESK .
There where two ships in the service with the Royal mail Line, the ESK (II) is depict on the stamp.
Built in 1882 as a steel passenger cargo vessel by the yard of Barrow Shipbuilding Co., Barrow for the Royal Mail Line, London.
Tonnage 2.145 gross, 1.374 net. Dim. 94.34 x 11.02 x 5.08m.
Powered by one compound inverted 2 cyls. steam-engine, manufactured by builder, 350 hp. speed 12 knots. One screw.
1882 Based at Barbados for the inter-island service.
08 May 1902, when St Pierre, Martinique was destroyed by the Mount Pelee eruption, the ESK was the first Royal Mail vessel to arrive off the coast, when approaching the steamship RORAIMA exploded and sank (she is now one of the best dive sides on the island). When the crew on board the ESK did not see any sign of life, she sailed to St Lucia for help.
The SOLENT of the same company arrived on 12 May 1902 with relief goods.
The ESK was broken up in 1910 on the Firth of Forth, England.
Source. Merchant Fleets, Royal Mail Line by Duncan Haws.