Dirk,
I agree with David Noble, get it checked out for low pressure shells.
I have an uplift hammer 12Ga made the same year. It was in HORRIBLE shape, MUCH worse than yours. My journey of restoration can be seen in this thread:
https://parkerguns.org/forums/showthread.php?t=32865. As one forum member framed it, it is a story of resurrection likened to Lazarus.
This forum helped me find a great restoration gunsmith in Ellijay, Ga, about an hour away from me. He measured and checked the barrels and proofed them with RST low pressure shells, even though the barrels looked awful inside from shooting black powder and little if any cleaning, YEARS ago (My dad found it in the attic of an old house he bought before I was born; I am 75). I hunted with it yesterday and looked down the barrels as I cleaned it up. They are not mirror clean, but it is quite notable that a couple of seasons of shooting has cleaned up a significant part of the junk. They are still not what a collector would look for, but neither is the gun, since it is a restoration, though a good one, and it is much more presentable. I don't have before pictures of the insides, but I hope to get access to a borescope and document the current condition.
Explore the low pressure option before going to sleeves.
Somewhat related, I have seen discussions here of using "Big 45 Frontier Metal Cleaner", a specialized analog to bronze wool, to also clean the inside of old barrels. I have not tried it, because I would like to get confirmation of its safety for old Damascus barrels. As gentle as it is on bluing, I suspect that it would be ok---But I want to make sure. If anyone here can speak to this, it may be also helpful for your project. I plan to post a separate thread on the question.
Nice Gun. Agree about gunsmith check for low pressure shells
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