At the Medina, Ohio show today, someone brought a Marx prototype and was showing it to the Marx parts dealer there. It
was a #21 A-A set refinished as Rock Island, similar to the plastic E-7's that were produced. This pair had the Marx factory prototype lable on it. Although the 21's are not my favorite Marx, although I'd bought a new pair when I was a kid, these were fairly attractive in the Rock Island livery, and definitely something not everyone has on their shelves.