They are rare. Restoration is fine, but the value will not increase enough to offset the cost of the restoration.
Is the stock ruined or does it just have the initials carved in it? If it's just the initials, I would leave it alone as part of the history of the gun.
I bought a 16 Ga. Model 12 a few weeks ago that had engraved on the left side of the receiver in block letters: "MIKE" over smaller block: XMAS-1928.

Ole Cowboy