WW2 37mm ammunition. What are the differences?

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I recently received a few WW2 37mm cases. I did not realize the standard 37mm AT gun of WW2 had a variant. The one in question has an M17 case. 
It is rimless, and a bit shorter than the common 37mm with an M13 case.

 

Very confusing, the 37 mm variant it appears was used in AA guns, and PT boats. Can anyone add more comprehensive information.

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Note: the previous owner filled the primer hole with a Russian 7.62 case and overseated the projectile past the driving band.

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More:

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More:I have confirmed this round was used in the AN-M9 cannon. Army usage dropped for the 40mm Bofors AA. In  June 1944 USN PT boats were equipped with the gun. 
 

From an Ordnance collector’s view, I suspect a rarer example? In 25 five years collecting, I have never seen one.

[ccyooper]

Nice find, I had a couple of them, sort of like the WWII 25mm Hotchkiss rounds. The Japanese used the rimless (AD guns) and the French used the rimmed in the MLE-34 etc. I don’t think I have any cases anymore as I have been downsizing and keeping mostly the tank ammunition. Obviously less common than the rimmed version. Regards.