I have seen many prototypes, pre-production concepts, solid models, working models, models never released and demonstrators whilst working at Parkers and from collectors. Although the Parker 25 seems to be very illusive when it comes to prototypes or even demonstrators. I have seen photos of prototypes but never seen a demonstrator.
Please contact me if you have any information on this topic.
The following are images gathered from sources and the internet.
Left: Maroon with black trim FP and BP with stamp.
Far right: Grey BP with black trim without stamp.
From an Ex Parker employee. All sold via an online auction in 2013;
Below: Is bigger better! A standard size stainless steel black trim flat top FP sits next to a 2:1 scale model. This actual one was on display at the LWES London Pen show 2013.
Left: Stainless steel 25 RB, with white trim, flat top. Prototype?
Right: Stainless steel BP barrel with a different finish on the bottom end. Possibly grey paint or shot blast.
Sold online auction May 2014 for $57.