Firstly, I must say that I have put some photographs on this topic from eBay.
Recently, a seller listed on eBay an unusual Waterman overlay which collectors often refer to as Tree Trunk. What was especially unusual about this overlay was that it was on ripple. I have only seen this overlap on black hard rubber.
The auction for this pen was ended.
My initial impression of that Parker Duofold is that it is a post production pen made using parts from a yellow and black Duofold. That said, the Tree Trunk seems genuine so I wonder whether the Duofold is also some sort of original pen.
Barry