Found on Tarawa near the new airport (the Japanese airport was on the south end of the atoll close to the main battle) the US military moved it to the islands elbow to enable a larger runway.
My guess is that your shell is an artifact of the 90MM AA guns, probably the M1A1 version, used by the Marine 2nd Defense Battalion. It landed on Tarawa on the last day of the fighting, November 24, 1943, and proceeded to set up its guns, searchlights and radar to protect the airfield which had been quickly brought back into service and improved. For the next three months the 2nd fended off 19 Japanese air raids attempting to strike the airfield.
The image below shows one of these Marine 90MM guns emplaced at Guadalcanal. This one belonged to the 3rd Defense Battalion. One of the projectiles can barely be seen at the left edge of the image.
A neat piece of Marine Corps history there.
Charlie, that is really fantastic information.
I have always wondered about the gun emplacements and in particular the large amount of 50 cal casings in the same vicinity. I had assumed they were practice firings as I hadn’t previously heard about the follow up attacks. All makes sense now.
Valuable information that I will print off and retain with the collection.