Mr. Vash:
If you resolve to buy a MN, then you will be much happier in the long-run if the bore is fairly bright and shiny. Some might have regular crud, or cosmoline. Be aware that the person on the phone might not have the time to clean it before you call him/her to ask about it.
And cleaning might not be their job. If you buy a gun from a private owner, store or gun show, this can be the better solution to your search.
Many of these bores suffer from corrosion because of soldiers/former owners who were careless or bums.
I have two MN 44s which look almost excellent on the outside, and the bores reflect a bit of light, BUT, the 'groups' at only 50 yards look like a group of sparrows in sloppy "fingertip" formation.
The groups are about 6-8 inches at only about 150 feet. A friend who is a qualified marksman tried out one, on his sand bags.
He still shoots with a military (reserve) rifle team, although retired, and never found holes for two of the rounds from one of my 44s.