Well i finally got around to tearing it all down.
It is indeed an M46 (thank you) & other than some badly drilled holes & a bit of filler (now filled & removed, blended & polished) is in great condition. For a project base, at any rate.
I do have another question though:
There is a missing screw that threads into the bottom of the rear sight base, through the forend. (See photo)
Can anyone tell me the thread size of this screw, or point me in the direction of where i could possibly find an original? I've searched every possibly parts terminology i can think of & I'm coming up blank.