Be extremely careful paying for historical value if your not an expert. People will fake the Nazi or US stamps on everything imaginable, and there are tons of low value guns like the Russian capture stuff than can be repurchased, and faked into a higher value. This isn't always an attempt to defraud, there are companies that sell these stamps for people who want a period "correct" replica down to the roll markings. Your usually fairly safe on anything not US or Nazi but just be very careful on paying for stories or historical value without documentation. Nobody in their right mind would ever fake a capture gun like a Soviet captured K98 or a Yugoslavia K98. So those tend to be the safest in terms of your probably not buying a forgery. But look for the keys, Soviet captured guns are almost always missing capture screws, or sight hoods, or sling mounts. So what's missing can tell you more than what's there.
Biggest thing that I'd say never buy are modifications or rare configuration guns. If there is a rare configuration rifle where they only made a thousand or 2, I wouldn't touch it with a 10ft pole without the documentation. They are magnets for forgeries.
As something I'd steer away from as a specific gun. I hate all things Mosin. The earlier guns are better, but I've had early 1940s guns that I had to smack bolts open with a 2x4 after a few shots and everything started heating up. They are easily the worse built quality rifles out there, and while they are worth a Benjamin to play around with, they literally are not worth anything more than that. They are truly horrible rifles. Don't buy them unless your just trying to fill out a collection. I just can't say enough bad things about them as the platform. The old saying was you could buy 5 Mosin for the price of a K98, but the K98 is genuinely 10x the gun. So ya, I'd say the Mosin as a platform is just awful compared to any other platform, don't buy them unless you just want a Soviet era gun that was built as cheaply as possible.
Also, the older pre-WW1 stuff can also be fun to collect if you dont want to shoot them a whole bunch. Built quality before the major wars jist seems to be across the board better. Wartime production will universally mean a lower build quality, and honestly doesn't add much. If you want a rifle used in combat, look for manufacture dates prior to conflict, and production within the final 1 to 2 years of a war means it had a much lower chance of being used in actual combat vs just captured at the end in a warehouse stockpile. This is fairly universal for all the major surplus guns.
