The secret decoder ring reveals its secrets.Hi
The Harleyford book, 'Spitfire - The Story of a Famous Fighter', despite being rather 'old' now does have some things of interest, including a list of Spitfire/Seafire 'variants':
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The book 'Spitfire, The History' has much more detail and drawings on many of these variants. The SAM Publications Modellers Datafiles No. 3 'The Supermarine Spitfire Part 1: Merlin Powered' and No. 5 'Part 2: Griffon-Powered' also have many of the 'official' drawings in that helps to illustrate the variations and improvements, including added fuel tanks and drag improvements.
Mike