"COUGARNFW" wrote in message
...

Having just read this last night...

The P-51's in america were P-51A, P-51B, P-51D, and so on whereas the same
plane for the brits would have been name, Mustang Mk I, MkII and so on.


Don't forget the P-51 itself. In the Army system at that time, the first
version of a basic design had no series letter, just the mission letter and
design number separated by a dash. Later versions had series letters after
the design number. P-51 was the first version, P-51A was the second.

The Mustang Mk.I in RAF service were North American Models NA-73 and NA-83,
there was no corresponding US Army designation.

The Mustang Mk.IA was the P-51.

The Mustang Mk.II was the P-51A.

The Mustang MK.III was the P-51B or P-51C, the British saw no reason to
distinguish between them.

The Mustang MK.IV was the P-51D.

The Mustang Mk.IVA was the P-51K.



The brits used roman numerals for their spitfires to denote different
models such as Mk VI and Mk VIII, but when they got to 20, they
gave up and went to 20 and and so on.


You're one off, the Spitfire Mk.XX was followed by the Spitfire 21.



Nothing was "pure" so the P-51C was exactly the same as the B, but built
in a different factory and, although the americans used the B or C, the
brits
called them the same "mark".


This is probably the best known example of a somewhat rare occurrence. Many
other aircraft in USAAF service were built in multiple factories by the same
manufacturer and even by other companies, but they usually didn't assign
other series letters to them. They just designated the factory/manufacturer
with a two letter code after the block number.

At least one aircraft had it both ways. Republic built the P-47D in
Farmingdale, NY, and in Evansville, IN. Farmingdale airplanes had -RE
following the block number while those built in Evansville used -RA.
Curtiss built Thunderbolts in Buffalo identical to the P-47D were designated
P-47G.

Interestingly, it was almost done again with the Mustang. P-51Ds built in
Dallas were initially to be designated P-51E, and P-51Hs built in Dallas
were to be designated P-51L or P-51M depending upon what version of the
V-1650 was installed. The P-51L was cancelled before any aircraft were
built, but one P-51M was built before the order was cancelled.