Okay, since 100 people have looked at this and nobody has guessed it...it's an ingenious little ASW device commonly called a "submarine hammer"
Once located with MAD, they would drop these things by the hundreds out of the ASW aircraft.
The way it worked was that they would sink and stick to the hull. That little flat spring looking thing in the curve caused it to turn and stick sitting upright. Notice the slight angle of the top aluminum piece...any water moving at all caused it to lift up and bang on the hull. For the guys stuck in the sub this was like being locked inside a big metal drain pipe and someone knocking on it with a hammer. Soviet subs didn't have divers on board so the only thing they could do was surface and pick the device off. Of course one of our ASW aircraft was conveniently passing overhead to take pictures as soon as the sub breached the surface.
The man that invented this thing was Bill Edwards. He was a mechanical engineer who was an employee of the Dept. of the Navy. He invented hundreds of neat things like this and was the Navy's "problem solver" for many years. He had many patents but they were all owned by the U.S. Navy.
I don't know how true this part is, but it is said that he invented the sub hammer in response to a Russian sub that would sit off the east coast of the U.S. in the early 60's. It would surface at night and run up a big antenna array and then ping up and down the band to interfere with encrypted teletype messages going out to our ships. One ping in the wrong place and the entire rest of the message was rendered unreadable.
The sub was nicknamed "the Russian woodpecker." The sub was sent in response to when Cuba was jamming signals down south and the U.S. put up a big array and jammed them back only much more powerful. Because the woodpecker was in international waters, there really wasn't much we could do about it...until we began pecking back with this little hammer. He wasn't long picking up and going home.
One of Mr. Edwards better known inventions was the blinking strobe light to ID aircraft...still in use today on just about every aircraft in the air.