While I'm at it, I figured I would post a better scan of the piece you pointed out. It didn't come out that well in the overall shot.
I don't know what this pin is...sweetheart? Official/unofficial piece of insignia?
As you well know, this particular design saw very limited use (what was it... a few months???). Then the Air Service adopted the much more familiar winged prop. Why, oh why, do so many variants exist of this design when it was only authorized for such a brief period of use?