Sonny B,
Cool example of something. I have no info about such a prototype. I have three other prototypes and two are marked with an X prefixed serial number. See attached pic. The third is the original prototype for the standard pistol. See attached pic. We have a few prototypes were Reising would use parts from other manufactures so it’s not unusual for him to build something like this. I can tell you it’s a Hartford Address gun because of where the serial number is located. No way of yet saying if Reising built it or a creative enthusiast.
I have seen ounce a pistol with a much longer than standard barrel. I would like to hear from someone who has one.
Glen