20x139mm drill ID

[US-Subs]

Looks very much like a US manufacture - but on a 20x139mm?

 

[Andy Naude]

My opinion is Lake City Arsenal. USA

 

[US-Subs]

Looks that way to me as well, but when was the US making 20x139?

 

[rigby]

This 20x139 Dummy is for the M139 cannon, a modified american Version of the HS-820 cannon.
I have a similar one.

 

[US-Subs]

Thanks, I had never noticed it previously. Wikipedia states:

The United States produced a slightly modified version of the HS.820 as the M139. It saw use on a number of vehicles, including the US Army's M114 and the Marine Corps Amphibious Assault Vehicle and the ill-fated MICV-65 series of armored vehicles, including on a palletised mount in the cabin of a Bell UH-1 helicopter.
A couple of related images from the internet: