Gun turret door

Evening all

Can anyone help me identify this turret door please? I am perplexed as most turret doors open outwards from the centre around the contours of the turret, this one appears to have been hinged. There are no stamps or markings as far as I can see.

[ATTACH=CONFIG]247686[/ATTACH][ATTACH=CONFIG]247687[/ATTACH]

Thanks
TEC