Steve, it's not on the Gretsch website.
Look at the links I gave just as an example for retailers above. Just go to their sites, and you will see the info. Just click on the links above. Again these are just a few examples.
Rupps info is, "proporionate maple/gumwood shells...maple/gumwood w/silver sealer"
Guitars Amps and Drums info is, "New Classic - Professional, retro-style drums set made of proportionate Maple/Gumwood shells with Silver Sealer interior." "USA Custom - Gretsch's flagship model. Professional, handcrafted drum set made of 6-ply Maple/Gumwood shells, with Silver Sealer interior."
Mass Music info is, "The Gretsch New Classic series drums are designed with classic looks and new modern features, the New Classic series is the first completely new-design set from Gretsch in over 50 years. Accented with vintage-styled tube lugs, the ITS integrated tension lug suspension system, and proporionate maple/gumwood shells, this series truly is a new classic for today's drummer.."