Very Rare WWII German Navy Pressure Egg

This is a very rare WWII German Navy issued pressure egg that was used by German Naval gunners to test the pressure of a charge. The pressure egg was placed within the shell, then after firing the egg would be removed from the spent cartridge and inspected, depending on the degree of distortion or damaged caused the gunner could then determine if he had the correct charged loaded. As a disposable non-reusable item very few are known to exist. This example has matching numbers and is dated 42 (1942) with the makers initials GW within a triangle. The lid is marked with German Kreigsmarine acceptance stamp. The numbers 52/8 are to indicate its size. The egg is made from steel and coated is a brass outer jacket.