FLYBOYJ
"THE GREAT GAZOO"
It's my understanding the RAF did not release 100 octane fuel for combat use until May 1940. So during 1939 a Spitfire I in combat condition will be topping out at 353 mph.
However, as has been pointed out the earlier Spitfires were lighter and thus faster:
and topped out at 367 mph.
Just for the record folks, we're splitting hairs here. As stated in earlier threads the 13 mph were talking here will hardly be noticeable in combat and having flown that fast I can tell you that you can barely push the stick forward and pick up 13 mph in a blink.
In these speed comparisons what needs to be examined is how quick said aircraft can accelerate to those top speeds advertised.
My 2 cents - stay away from the stock market....