You've seen this?
https://www.amazon.com/Harmon-TYLER-SPINDLE-ACTION-SHOTGUN-Report/dp/B09FT2953L

The seller's pics are very small but I think the pattern in 3 Iron Oxford. Post a better close up full size image of about 8" of barrel when you get the gun and I'll read the pattern. With that contrast the barrels may have been refinished.

If you'd share the chamber length, and end of chamber, 9" and minimal wall thickness and location thereof several here could provide an opinion regarding load pressures. IMHO a vintage double without pitting means honing.

https://sites.google.com/a/damascusknowledge.com/www/home