If you can run some dummy rounds through it before buying to at least see that it feeds and ejects properly would be a big plus. Live fire even better. They can and do have problems that you can't see by just looking at them and working the action. They are complicated mechanisms with alot of parts that have to all work together perfectly to make for a smoothly timed action.
They're great shotguns when they work correctly, but an expensive pain to repair when they do not. Parts are pricey and most are worn, being salvaged from worn out guns themselves. Several slight changes in the internal parts can make it a challenge to fix sometimes.
They all have the so called 'slam fire' feature which in reality isn't as the bolt is locked before the hammer falls & strikes the fireing pin,,but it is neat feature. M12's and M42's also had it.
The fireing pin can break & the tip jam in the forward position dispite the retraction bar and it can fire upon closing the action without it being locked. It will then fly open causing some damage most likely to the action and the shooter. Not a very common occurance.
I've owned several,,still have 2 of them. Both made in 1903. They have fired several 1000 rounds each by me and other than replaceing the ejector once each with a new repro and a good complete strip/clean every 6 months or so, very little has gone wrong.
I've lightened the mainspring tension to lessen the upward push on the bolt from the hammer when cycling the action. It makes for a really slick working action and reduces the wear on the receiver ways where the bolt rides when fully retracted. Never any misfire problems.
I sold a 12ga full choke, solid frame 97 not too awful long ago. I had bought it for $250 at a show and was suprised no one hadn't grabbed it before me. Had thoughts of Riot Gun for it but got talked out of it and it's still in it's original configuration. I see it almost every week at the skeet range and it really reaches out there!
I too seem to recall that 20" was the shortest they made,, then 26" (Brush gun). Might be wrong,,,maybe some info in one of the big winchester books.