Know that the early 7mm cartridges were not the same. One was slightly longer than the other. Rolling blocks can be found in both, and you have to determine which one your potential purchase is chambered for. Firing modern ammo in a rifle chambered for the longer case will result in a case that is horribly stretched to near the point of failure. I had one of these, years ago which I sold for parts. A quick test is to chamber a round and see if the rear of the case is exactly flush with the rear of the chamber. If it appears to sit .010" or so below the rear of the chamber it is probably chambered for the wrong cartridge. The only real way to be sure is to fire a round of ammo and see if the case looks normal. The early UMCC rounds in the pic worked fine in my early roller, which was chambered for the longer round. For what it's worth, my current gun is stamped, " CAL. 7mm. " on top of the barrel just ahead of the wood. My earlier gun had no stamp. If your prospective purchase has this stamp, I suspect it is good to go.
Having said that, the smokeless powder 1897 and 1902 rolling blocks are very desirable and sought after by BPCR competitors. The action is capable of digesting 45,000 PSI cartridges, and were chambered in 30-30, 30-40, 7.65 Argentine, 8mm Lebel, 7.62X54 Russian and .303 British in addition to 7mm Mauser. Despite what WIKI says, they were never chambered in 30-06.
These guns had a very fast twist and deep rifling. They are rarely found with a mint bore. Mine is a bit dark, with moderate pitting the entire length of the bore. It shoots just fine. It still has a bit of case hardening color visible on the action. Notice the screw heads, all pristine. If they are buggered up someone has been at work with an ill fitted screwdriver. There was no reason to disassemble these guns unless a spring broke. As one can see in the pics, mine is in average, well used but not abused condition. There is some parts overlap between between the 1897 and 1902 versions. Mine has the 1897 rear sight and the 1902 fore end cap. The 1902s had a ladder rear sight.
These guns had no serial numbers.
If you lean toward the Chilean Mauser, make sure the bolt matches. It was common for South American dictators to store the bolts separate from the guns, serial numbers be damned. I have a nice Chilean, with a mismatched bolt. If yours has one demand that the seller lower the price. .