WW II German Torpedo Aiming Calculator

I got this and two other pieces from a man who bought them many years ago at a house sale. I have owned them for nearly twenty years now. They were taken off a surrendered German u boat near the end of the war. This piece is all brass and is dated 1937. It was used to calculate a torpedo's run to a target. It also has the original oak storage case. Both pieces have matching serial numbers. During this time, Germany was secretely testing various submarine designs. I have been collecting militaria since 1975 and have never seen another one in person or a reference book. Your comments are welcome.