I recently came into possession of this slide:
Factory Experimental 5906 Slide
Factory Experimental 5906 Lever
and several others, plus some parts that also appear to have been crafted in/by the Smith & Wesson Model Shop (also known as the Experimental Shop) around the time of the transition from 2nd to 3rd gen.
I would love to share them with the Forum, but first I would like to contact the original owner and author of the linked thread, Dave Nash.
I can't PM him because his mailbox is full and I don't have his e-mail address or phone number.
If you know or can contact Dave Nash, please put him in touch with me.
Just a teaser:
The first experimental 4516
The first experimental DAO
Dave Nash can verify.