Looking at a 52:
The ringed barrel issue can and does happen when a foolish handloader either makes ammo that is too light, sticks a bullet AND then shoots another bullet behind it. The other way it happens is running too hot a load with soft swaged HBWC bullets — the core blows out and the outer ring of bullet remains and the follow-up shot is now greatly over pressure and the barrel gets ringed.
Personally, I'd LOVE to find a 52 with a ringed barrel -IF- it was priced properly. $500 and I'm thrilled, Clark Custom makes a replacement barrel that may possibly be better and has a twist rate better suited to longer distance shooting where the 52 as originally designed has issues stabilizing the bullet.
Some have complained that the trigger on a 52 doesn't always make "legal" weight for competition and it can be difficult to manipulate the sear spring to make the trigger heavy enough. Not a deal breaker, but this exists.
If you look at the MSH, you may find that however they finished this part is NOT very durable when it comes to fighting sweat and skin oils. Many 52's quickly show wear in this area. It's only a finish issue, doesn't affect function.
The bushing is a great design but the threads are extremely fine and a ham-fisted owner could cross thread them and torch 'em. There will NEVER be a reason to torque that bushing down with gorilla strength but it happens a lot. The included "bushing wrench" is complete trash and should literally never be used on a 52 bushing for twisting in either direction. It is stamped sheet metal and this wrench is an abomination. If a prospective purchase doesn't include one, good.
Magazines were often altered to hold more than five rounds. Some tinkerers were better at this than others. Magazines for this pistol currently carry a ridiculous price tag. Even a poorly altered magazine should hopefully still work with the original 5-round capacity.
If you see circles on the frame around the slide stop hole — that's almost certainly evidence of a frame mounted scope rail. These marks are ugly but they don't hurt anything.
Some 52's will show wear by exhibiting hammer follow. While letting a slide slam home with a totally empty chamber isn't friendly gun handling in general, it is the method that many builders use to manually check for hammer follow if you aren't able to live fire the pistol. A few times dropping the slide isn't going to hurt anything and it may show you if there is hammer follow. If there is, it is fixable but takes some skill.
My first 52 was a game changer for me, and an INSTANT REGRET! Sorry, that was a cheap misdirect. I emptied my first five shot magazine and my first emotion was to beat myself about the head for waiting this long in my life to buy one. My second emotion was "dammit, this gun is out of production so owning just this one isn't enough."
So I have three. I'm probably not done.