Genuine original parts made during WW2 for Spitfires and Hurricanes are becoming increasingly rare and sought after when they are either new or unused and especially so when they are stamped with the Kings Crown and AM.
Occasionally I come across gauges embossed with the Kings Crown & AM rather than the WD arrow and this is one I've found amongst our stock of boost gauges which we have held for 40 years.
This particular one is dated 1943.
If you really want to be absolutely sure of getting a gauge with the Kings Crown then this is it.
Looking at the photos you will see that the mounting lugs are perfectly clean and unmarked having no  "witness marks" proving this is a new/unused original genuine gauge.
The spacing of mounting holes are 2.125" centres and the threaded male connection diameter is .383" o/all (1/8" BSP)
Genuine and original pieces of WW2 aviation history are becoming rarer and hard to find and once my stock is depleted there will be no more.
I do still have some Boost gauges still in wax sealed boxes which at the end of WW2 were destined for the far east but never sent. These boxes remain sealed just as they were 75 years ago and it will either be marked with the WD arrow or the Kings Crown but I cannot say which.

This might be the last new original stock boost gauge with the Crown & AM so why bother to pay as much for a replica gauge when you can have an original part from the RAF stores?
Just like the Spitfire these will only increase in value as time passes.