Early 1897s were chambered in 2 9/16ths. I have an 1897 that will only work properly with 2 1/2" shells. But, with 2 1/2" shells, it functions flawlessly. Early '97s were also solid frame (as is the military trench gun version). Those since very early in the 1900s are take-down.
I have 4 1897s that work fine with 2 3/4" shells. Most (but not all) 1897s chambered in 2 3/4 will have 2 3/4 stamped on the barrel. No '97s were EVER chambered in anything longer than 2 3/4" so, yes, you can forget about 3 or 3 1/2" magnum. These guns are not for steel shot, anyway; the barrels were never intended for steel, and the overwhelming majority of them are full choked.
When evaluating one, you should load a 2 3/4 inch snap cap in the chamber and 2 in the magasine (while you're at it, check to make sure 3 shells don't fit in the magasine). Drop the hammer on the snap cap and cycle the action. The "spent" shell should extract and eject cleanly and the carrier should carry a fresh snap cap into the chamber. Repeat. All 3 shells should eject. If the chambered shell doesn't extract, or shells get "tangled" in the carrier, the gun probably needs extractors or ejectors. The work will cost what the gun's worth.
Cycling and firing live shells is much preferred, but obviously not always possible.
Dark black staining of the stock just behind the receiver is caused by oil leaking down into the wood when the gun is stored vertically. Badly stained stocks and/or stocks with cracking should be avoided. You can replace the stock easily enough (and many have already been done), but adjust the purchase price down to cover the work.
Watch for looseness between the receiver and the barrel/magasine assembly. If any exists, it can usually be adjusted out, but you should check the adjustment sleeve to see how much it has already been adjusted. There are 5 adjustment sleeves in all, each one with enough adjustment to offset a significant amount of looseness. Even with mild abuse, these guns should last hundreds of years. A good number of them have already passed their first centennial.
