Measure the bore diameter carefully in two places at 90 degrees to each other. The most wear is at the bottom of the bore. Should be 2.391" to 2.411" across.
Also check the thread pitch and diameter. There were a lot of makers of the 60mm type guns and some are metric while ours are of course SAE. I don't have the thread spec here but I can get it pretty quick. I do know the chinese built guns have threads that are very close to an SAE size. The outer tube diameter is the same across the variety of makers because the clamp for the bipod has the same bore. Not sure why they kept that so close but they did. I use a Yugoslav bipod on my M2 because I don't have to worry about scratching up my like new US M5 1945 dated bipod. The clamp does not have much room for variation in tube diameter so it has to be close. I can get that diameter tomorrow too....
As for the shoulder above the threads its not a significant marker for any particular type of barrel. I've seen US tubes with that shoulder and I've seen US tubes without. The chinese tubes sometimes had them too and I'm not sure about the yugo or other east bloc types. The thread pitch and diameter will be the easiest to check and it will be the most likely to nail down origin.
Thread is called out as 2.837"-12 for the US gun so the 12 tpi sounds right. Your diameter is a little bigger but not a lot. Not sure of the metric callout.
Tube outer diameter is 1.743"-1.747". Any bigger and the clamp won't fit, any smaller and it won't tighten up.
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