HMS Clyde and HMS Severn were two Thames class submarines.HMS Clyde was the first ocean going submarine to exceed 21 knots. HMS Severn was launched in January 1934 and completed in February the following year. HMS Clyde was laid down two months later and also completed two months later. Armed with 1-4 inch gun, 2 machine guns and 6-21 inch torpedo tubes they were capable of 22.5 knots on the surface and 10 knots submerged.
The stamps have been printed by Walsall Security Printers on CA special watermarked paper by the lithographic process. Printed in sheets of 50 made up of 2 panes of 25 separated by a &utter they measure 25.6 x 38.48 mm
Gibraltar Philatelic.
Gibraltar SG592