Frogs

The Ruby Contraband was first shown when Dave began an alchemizing session. It was given to him by Future Dave. The item resembles a ruby frog; a red version of the ILLEGAL CONTRABAND found on the Land of Wind and Shade.

Alchemizing
Dave has tried to use the Ruby Contraband once, so far, during his first alchemizing session, in conjuncture with the Caledscratch, but the result of this alchemization, the Scarlet Ribbitar has proved to be far to expensive to create, for the time being.

Theories and Speculation
Frogs, and other amphibians have been shown to be a reoccuring theme in Homestuck. This includes the Frog Temple found on Jade's Island and the Cherished Idols found on the Land of Wind and Shade. It is therefore likely Dave found this item, along with some amphibians on the Land of Heat and Clockwork.