Marx Monon Motor Mystery

My first attempt at narration! Maybe my last. This is a Marx mystery, at least to me. I picked up this engine on eBay for the B-unit that came with it. It wasn't until I unpacked it that I realized it was significantly different from the one I already owned. I checked with one of my Marx friends who had heard of this variation (using KCS black frames) but had never actually seen one. Any help from viewers would be greatly appreciated. Here's a link with more information, thanks to Lionel0824: http://www.toyandtrainguides.com/marx... Click on Diesels and then Monon Clockwork Diesel.