A Curious SHTLE III*

I recently won a No 1 MK III* at an auction in Yellow Spring, WV.
I was bidding on the rifle because it was from 1917 and in excellent shape.
All numbers match, even the follower on the magazine (I believe) and the bore is excellent.
All mechanics work as they should.
Rifle cycles 303 brass as it should (I've not fired it yet.)
The only markings on the stock is a shallow stamping of "J.G." on the left side.
Stock disk is present but bare and painted black.

From other Enfield people I believe the "C.R." royal cipher is actually "G.R." from a worn die.

Once I got home I saw the "U S" markings on the collar and receiver.
I've got a couple of Khyber Pass rifles from my youth and this one just does not feel like one.
Just to much detail that appears appropriately worn for age.

Not sure how to include my images with this question.

In any case, can anyone tell me what this may be ?

Many thanks.

It looks like a rather nice SMLE Mk III* made at RSAF Enfield in 1917, using some parts intended for the earlier Mk III model (the foreend is scalloped for a volley sight, the cocking piece is the round type rather than the flat one, and it still has a brass unit disc in the stock). This was extremely common, and one of things that makes studying these old rifles so fascinating.

I haven't seen the US markings on a Mk III/* before but I recall some US soldiers were issued the rifles in the early days of their involvement in WWI so it's possible this is one of them? Hopefully someone will have some more insights to offer there.