I had one of the original run Jag-Stangs back in the nineties. That one did not have a coil split option, so I had a push pull pot added. With the bucker split, it did a great Straty "in-between" setting with both pups engaged, which is what I am going for with the split switch I want added to my Mustang.
I noticed the serial number thing too. But I am assuming (could be totally wrong) that prototype models do not adhere to any production serial number stamping and standards. The listing also says the serial number is stamped on the neckplate which is not standard for the production run. As you know the serials are stamped on the back of the neck above the neck joint.
This guitar and included material in this auction is essentially what was on display at the Fender Museum. Fender Museum of the Arts Foundation is noted as providing provenance.
Back in 2008 a forum user sent us some photos (link and photos below) from the Fender Museum exhibit. And the exhibit included the prototype guitar, drawing, and the body shape cutouts. These look like the same cutouts and design drawing. The lack of more detailed guitar photos is disappointing though.
Prototype jag-stang at Fender Museum [blog link]