Looks like a vinyl sticker applied to both sides over some kind of fiber board. One picture shows a crease in the graphic.
Was in when I bought it and it still displays great. Look for some very rare nos decks!! The item "Sims Kevin Staab Tortuga Shipwreck Tribute Deck.Very Cool" is in sale since Wednesday, February 01, 2017. This item is in the category "Sporting Goods\Outdoor Sports\Skateboarding & Longboarding\Vintage". The seller is "acuracl13" and is located in Holland, New York. This item can be shipped to United States, to Canada, to United Kingdom, DK, RO, SK, BG, CZ, FI, HU, LV, LT, MT, EE, to Australia, GR, PT, CY, SI, to Japan, to China, SE, KR, ID, to Taiwan, ZA, TH, to Belgium, to France, to Hong Kong, to Ireland, to Netherlands, PL, to Spain, to Italy, to Germany, to Austria, RU, IL, to Mexico, to New Zealand, SG, to Switzerland, NO, SA, UA, AE, QA, KW, BH, HR, MY, BR, CL, CO, CR, DO, PA, TT, GT, SV, HN, JM.