Terminology - Tropical
When the war extended into Africa, and other hot and humid environments,
it was discovered that the humidity had a tendancy to penetrate the cartridges
and render the powders inert. To counter this, special manufacturing methods
were used to seal the cartridge at the mouth and primer pocket. These rounds
were either marked "Tp" to denote the modification or a bright colored
dye was used in the sealing material to identify it.