Nice sauce pan, Including my skillet that makes a total of 3 Castelain Made in USA pieces I have seen, Mine here in NJ, an eBay auction from Brookly NY and yours from Buffalo NY, I am wondering if the geographical location of the foundry may have been in this area (NY/NJ) Besides Castelain made in the USA is there any other markings on your pan, My skillet has K2 incised on the bottom, All of the other markings are raised and the K2 is cut into the bottom of the skillet and I believe the eBay piece also had the letter K incised into the bottom.
As for mediablasting to remove paint I think it depends on what type of media you use as far as if it would damage the surface, sand would be a definite no but walnut shells, corn cob or acrylic or some other type of material that is softer than the cast iron should not be a problem that I can see, If it does not actually cut or etch the cast iron and only cleans it then it should not damage the cast iron surface, hard sands and oxides actually cut the cast iron and leave a dull grey surface which is not desirable.