You can't always go by Mr. Cook's book...although it's great, there are some errors, like that about the 13" snares. The drum you have is rare, but I doubt it was a custom order. Most of them were 3 ply, but solid shell ones do exist. I'd guess your drum would get at least $500.
Until the 1980s or so, most drummers had no idea what type of shell they were getting...it was either wood or metal. Even though Slingerland listed a lot of their drums in their catalog as solid shell models, thousands of them went out with 3 ply shells, and nobody noticed. I've yet to see any proof of anyone ever ordering a particular type shell.
