The first Crawler box or should I say Dual Cases was however not invented by Marlin. Marlin is responsible for his own 4.7 gears however
the First Dual case was invented by a guy in Ice Land which Marlin spoke with and after ordering one, Marlin started making his own. So in that respect Marlin was not the first.   (I did not make up the above mentioned, I was told this story by Marlin him self, so if you don’t like it to bad)