Pearl stocks often contain embedded salts which can corrode the frame over time which is another possibility for them sticking to the frame. I find that tapping on the screw sometimes pops out the escutcheon in the stock, so I use a single edged razor blade, push it in between the stock and the frame on the very bottom of the frame. Once inserted, tap with a screwdriver handle and the stock should loosen easily. If not, move the blade to the lower front corner and repeat.
Smith & Wesson offered pearl stocks dating back well into the 1800s. They were made to the same thickness of the factory wood or hard rubber stocks. Distributors found that they could buy or make thinner pearls and place them on revolvers. It is very likely that the customers did not know, so many complaints about poor fitting thin pearls came back to the factory. They also placed labels inside their boxes to alert the customers to only buy medallion pearls. S&W started installing their trademarked medallions in pearl and ivory stocks around 1898. The factory stopped making pearl stocks in the teens and then worked off inventory until the early 1920s for some models. It is also known that pearls were reintroduced for a very short time in the 1930s, but S&W stated they could no longer rely on obtaining quality mother-of-pearl for stocks, so ceased production.
The revolver is not in great shape. Without the pearls, the gun might be worth $250- $300. The stocks by themselves could be in same price range.