You say your gun was made in 1925, so it is now 100 years old. If you have the chance, take a look at the head inletting of several old L.C. Smith shotguns. There isn't much wood bearing against the frame to take a lot of battering from excessive recoil. Many of these stocks will already have cracks from recoil, stock design, and the brittle nature of the old wood.
If your 3" chambered barrels are sound and unpitted, they would probably survive firing with modern 3" Magnum loads, but no guarantees. I've mentioned the brother of a friend who frequently fired 3" Magnum loads in his Dad's 20 ga. L.C. Smith Field Featherweight. He seemed to get away with it, but removing the stock could tell a different story. I'd be a lot more concerned about the wood. Chamber pressure doesn't crack wood, but the recoil of modern Magnum loads certainly can. You won't know for sure until the damage is done.
As for current value, your best bet would be to follow ACTUAL SALES of the same gun in similar condition on GunBroker, etc. I'd guess around $800.00 to $1000.00, but I haven't really followed L.C. Smith prices for awhile. I can confidently say it will be worth less with a damaged stock. I have a bunch of old doubles, but I also have some modern guns that I can use to burn modern high velocity ammo. You can buy a suitable gun for less than the cost of repairing or restocking your 100 year old Ideal Grade.
