Big Caseih combine seen towing grain cart

First of all I apologize for having no photos, but I saw what looked like from a distance as a 9230 with tracks towing a grain cart with tracks. It was a pretty good ways away but I could definetly tell it was pulling the cart. The combine was harvesting rice about 20 miles from my house. Have any of you guys seen anything like this on new combines? I'm sure its some kind of caseih prototype and a high yielding rice field, with lots of mud would be a good place to test its toughness.