The Highest Possible has been a very elusive item, perhaps because so few were ever made which then had to survive the next 100 years. I have no exact records of the production figures but the Collectors Guide to Air Pistols by Dennis Hiller suggests that the highest serial number known is 1052 suggesting only 1000 odd were ever made.

Engraved on the L.H.S of the air chamber "WESTLEY RICHARDS HIGHEST POSSIBLE - AIR PISTOL". On the frame near the sear is stamped the serial number, 369, which also appears on various other parts. On the left side of the frame is engraved "WESTLEY RICHARDS & CO. - LONDON W" and near the action latch appears "PATENT 24837 1907". The pistol has black chequered vulcanite grips and a 9 3/4 inch rifled barrel. Rear sight appears to be adjustable for elevation only. Length from tip of barrel to base of butt is 12 1/4 inches. The above design was patented by E. Anson, a relative of W. Anson of the well known partnership Anson & Deeley. The "Highest Possible" was also available nickel plated. Highest serial number seen is 1052. Inside of grips are usually scratched with the serial number of part of it and the rifling appears to be anticlockwise. ( From Air Pistols by Dennis Hiller)
The above sequence of photographs shows the cocking of the air pistol.

Peter on August 9, 2016 at 1:57 pm
Hi Simon,
What a fine pistol that is, looks to be in unrestored condition, someone has taken good care of it over the years, it looks to have been much loved.
But what about that “Holster” it fits the pistol like a glove, it’s certainly rarer than the pistol itself !
Did “Westley Richards” retail the Holster ?
In the advertisement that begins the blog, it shows a cased pistol with everything needed, but I see no mention of any holster.
Now I know the configuration of the holster I will certainly keep both my eyes open.
Great Blog,
All the topics that arise from your meanderings seem to stimulate interest, keep it up !
Regards. Pete.
Vaughan Condron on June 10, 2016 at 5:41 pm
Dear Mr Clode,
I don’t want to dispute Dennis Hiller’s work, but I have a Highest Possible with serial number 1153.
It has the same patent number and functions, but the finish is not quite as well preserved as your example.
I thought you may find this an interesting part of the Westley Richards’ story.
Kind regards,
Vaughan Condron
Simon Clode on June 10, 2016 at 6:22 pm
Thank you, I think that is indisputable! Someone pulled me up about a date I put in our recent little catalogue to which I replied “I must be right as I wrote this catalogue” the fact that I had sent him a rifle history that dated his rifle was made 3 years before I mistakenly said the cartridge was introduced!
Peter on August 9, 2016 at 4:41 pm
Simon
Thank you for your reply.
What a pity it could have been a quest for the “Holy Grail”of Holsters.
Pete.
Simon Clode on August 9, 2016 at 3:55 pm
No, I think this was just a hand made holster by the owner. I don’t think it is anything that we made.
Thanks for you kind comments on the blog!