just bought this p-METER which is said to come from the German submarine u 3503
That did sink in Sweden
On 6 May, 1945 at 07.50hrs, U-3503 entered Swedish waters west of Gothenburg. The commander, Oberleutnant zur see Hugo Deiring, reported a defective exhaust valve and rudder engine, and that some crew members had become poisoned by the fumes. On 7 May the Swedish authorities ordered Deiring to transfer the U-boat shallower water north of the inlet to Gothenburg harbor.
On 8 May at 17.22hrs, Deiring reported that his ship was sinking. The ballast tank flood valves had been opened! Attempts made by the Swedish Navy to tow the U-boat were not well-received by the German crew, who threw the tow cable overboard. At 19.50hrs, the entire crew abandoned the U-boat and was picked up by the Swedish Navy. At 19.55, the U-3503 sank at a depth of 15 meters.