I have the sister to this 2" target scope, made by the J [John] Unertl Optical Co, with both the early blued mounts and the later POSA-style alloy mounts shown here. Value in the USA is around $800-1000. THE Unertl maven is Dewayne Greiner. Google his site under Unertl scopes and he'll put you right -
http://unertl.alexweb.net/
Scopes were made in 1", 1.25", 1.5" and 2" diameter objects, in many different magnifications from x6 up to x36. Mine, made in 1952, is a x18.
As for what it went on, only the x8 version went on the '03, and they are all clearly marked with the property mark of the USMC. If you have such a scope, be warned that there are fakes around - the real deal is worth well-north of $5000 - I've seen one for $12,500, although there WAS a '03 hanging underneath it.
YOU can put it whatever you like - mine is currently on a BSA Martini MkII International, but they are bomb-proof - put it on a centre-fire, as I'm about to on my High Wall, and laff. You'll need the special POSA-style cut-away mounting blocks, BTW, if you don't have them already. Mr Greiner has them, as well as other accessories.
I'm sending a pal here a pic of it installed [sans recoil spring - not needed on a .22LR] so that he can, if he will, post the image for you to see.
tac
PS - Mrs tac has just reminded me that there are also frawks of THIS type of Unertl scope, as put on a replication of the the '03 by the 'Gibbs Rifle Company'. Trust me on this one, they are NO Unertl - the real deal - like mine, is a peerless chunk of optics, even at the age it is. It really is like looking through the very best scope you've ever looked through in your life - .22LR holes are clearly visible at 100m.