Well I managed to track down the aircraft it came off of.
It is an access flap for the upper wing surface of a supermarine spitfire. It is situated on both wing surfaces between the flaps and the fuselage.
See images below.
Photos: Supermarine 365 Spitfire PR11 Aircraft Pictures |...
Found this aircraft access hatch in the workshop and wondering what it was used for and maybe what aircraft it came off of. See photos in link below.
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Markings are E191316-2 and R/84 and N 21 0
Flush rivetting.
Was from a WW2 aircraft wreck in Northern Terrirory of Australia...