How can we tell the lock up is bad on the Stevens shotgun from just looking at pictures?
What SxS said for the most part.
While we can't tell if it's truly off face, in my experience, when the lever is that far to the left (touching wood or well past) it's been shot with poor lockup long enough that it's usually worn down the pin or hook face enough that it'll rattle at the face of the breech with the forend off if you shake it by the barrels.
The steps to checking out old SxS shotguns are to:
- Check the lever position. You want 6 o'clock to 5 o'clock. Later than 6 means it'll need work soon
- Remove the forend, grab it by the barrels, and give it a wobble. If it rattles, it's off face.
- Holding the barrels by the hook with one finger (resting the hook on the finger and letting the barrels dangle down) use your fingernail or a small mallet or piece of wood and ring the barrels like a bell. If they sound bright like bells, the soldering is good. If they clunk and sound muffled, the joining is bad and the barrels will need to be re-soldered. That's $$$$$
- Now look on the ground and at the face of the hook. If there's a slip of paper that fell out when you took the forend off, or mashed into the hook, remove it, put the forend back on, and check the lever. It moved to the left most likely. This is an old dealer trick to make a shotgun look like it has more life in it than it actually does. The paper pushes the action together more making it seem on face and with proper lockup. It's not often you see this, but something to be aware of.
- Look at the rib. Is there any solder missing? is it loose anywhere? Has the gun been cut down at some point and the rib is now lose at the muzzle end? If so, it's going to have to be re-laid. $$$$$$$
- Check the stock for cracks or chips and poor fitting where it meets the action. This can be another sign of it being off face or out of lockup like SxS mentioned.
There's plenty more, but those are the basics and deal breakers for the most part (unless it's a LC Smith, Fox, Parker, etc. that would be worth spending restoration money on).
Midway USA had an interesting series on doubleguns a while back. All types of restorations.