I have a silver coin dated 1939 that says one penny...?

I have a silver coin dated 1939 that says one penny with a soldier sitting down next to the British flag holding a 3 prong triton on one side. The other side says Georgivs VI D. G. Br. Omn Rex F. D. Ind IMP and has a portrait of a male. What is this coin and how much is it worth today?