Short answers, pulled from the story.
The Mark 24 mine entered service with the Allies in March 1943. The United States Navy received first production models during this month after testing of pre-production prototypes continued into December 1942.
The Mark 24 mine sank a total of 37 submarines combining German and Japanese targets. This figure includes 31 German U-boats and 6 Japanese submarines among the total count.
The Mark 24 mine measured 84 inches or 2.13 meters in length with a diameter of 19 inches or 48 centimeters. It weighed 680 pounds or 308 kilograms while carrying a warhead containing 92 pounds or 41.7 kilograms of HBX high explosive.
General Electric designed and fabricated the propulsion and steering motors for the Mark 24 mine. A 7.5 hp off-the-shelf General Electric Washing Machine electric motor drove the single propeller using power from a 48 volt lead acid battery.
Two engagements in May 1943 claim the first U-boat sunk by the Mark 24 mine. On the 14th of May 1943, a USN Catalina sank Kemp p117 or Neistle p78.