UNIQUE WESTERN ELECTRIC 335W TRANSMITTER HOUSING-PURPOSE UNKNOWN

Description

Offered is this unique item made by Western Electric, marked 335W which I believe is a transmitter housing.
Documentation on the 'net shows a number of transmitter numbers in the 300 range, but this number doesn't appear, but that would put it into the teens or twenties.
The body is bronze, the octagonal cap is brass, and the diaphragm is  rubber.  Overall, it is about 4-3/8 inches high, 3-1/2 inches wide, and about 2-1/2 inches deep. It weighs about 3 pounds, so it is quite heavy for its size. The mounting flange on the bottom is 2-1/2 inches in diameter, and has 12 mounting holes in addition to the pipe thread in the center.
The rubber diaphragm is around 1/4 inch thick.  It is rock hard now and cracked from age. The terminals inside the shell have never been soldered to, so this was never actually used.
So what was the purpose of this? It's clear that it was intended for a severe environment, perhaps military. If military, then it was probably naval. A submarine perhaps? Everything about it suggests it was designed to withstand a significant pressure differential with leakage and corrosion a concern.
Was it ever produced, or is it an experimental unit or a prototype? Is it a one-of-a-kind?
I really don't know, and the person I bought this from had no idea either.  He was a collector of railroadiana, if that offers any clues.
The condition is as you see it.  Unfortunately the cap appears to have been "restored" with a wire brush by someone in the past.
I will let the next owner decide what it is.
Thank you for looking!