This box is made of gasoline-soaked balsa wood. It's a really bad design. If it gets lit on fire, it will burn up instantly. A few selected items can be tempered by fire though. Perhaps you could store them inside and see what happens when it burns?
Highly Combustible Box price in Growtopia: sells for about 3 WL (median of 38 offers from community Discords, past 30 days). Live price chart and the latest buy and sell offers.
Recently sold at: SAMBALGACOAN, FEL, TUZOL, NVA, YAPI