I think the X7 and XT-22 are made in Mayfield, KY and not Ilion, NY.
Current production may have gone to Mayfield, alone; but production was shared in the past. Both Ilion and Mayfield were producing X7s.
As far as JM stamps, I guess it's possible that there was some overlap.
Yep. It goes both ways.
Marlin was using some "REP" barrels, before they shut down in CT.
And, Remington was still using some "JM" barrels in Ilion.
There's no easy way to figure out what you've got.
The only thing that really matters.... Do they shoot?
(Edited a ridiculous typo.