One thing I noticed is that the barrel on your 7mm has the proof mark on top. On my two pre-64 barrels, at least - a '51 and a '56 - the proof is on the left side. The caliber on those barrels is also stamped in front of the date. That's missing on your barrel.
I also agree that the roll marks are not consistent with a pre-64 barrel, and that the pre-64 front ramp would be soldered on, not screwed on.
That "55" might just be a red herring. Or it could be the barrel length. 55cm is real close to 22".
I'm inclined to go along with the European market idea. When I was stationed in Europe in the mid 70's, the military Rod & Gun Clubs would occassionally get American-manufactured rifles in oddball Continental calibers. Maybe it's a bring-back!
