Regarding the 'Out of Service' signs, it's just me being over cautious being marked up in Battenburg! I have a strict code of conduct to follow which is outlined by the Association of Chief Police Officers and I carry a letter of endorsement signed by it's Chief Constable, I have also informed the Chief Constable of Lincolnshire and Thames Valley of it's exsistance. It also pays to be a member of either PVEC or PCUK.
The rear board is done for a reason, the equipment fitted by Thames Valley Police was on various locations in the back of the estate, but my reason fitting one board was so that I can fit a dog cage in the back which allows us as a family to go to various shows up and down the country, and adapt to running a preserved Police can in today's world. All Police equipment has to be isolated as can be seen by the red switch on the rear board.
So Paul, I can supply info on the Battenburg, and if you wish to send me a PM I will supply my contact details.
Your car sounds interesting, any photo's!