The HK P7 bears a striking reselblence to the operation of the Gardenia (I think) garden hose nozzle.
It's a wonderful bit of engineering. The NJSP had these for a while but moved away from them due to ADs - probably something having to do with squeezing with 3 fingers to cock, but not squeezing with the 4th. Another problem is they make a loud "click" when cocking or uncocking, which can be a problem if you have to discretely make the gun ready, or if you are surrendering to armed police who respond to you holding someone at gunpoint.
All in all, I'd love one in my collection, but not at $2500 - although the one in the classified is a nice sample. I don't buy into the Chantilly marking adding value, but what does add value is that it is not one of those police trade ins with the agency name milled out of the slide.