This is metal on wood and measures 9" x 6 1/2". Condition is excellent. I have no idea on its origins but as I understand it OCA stands for Offensive Counter Air. This is obviously a New Zealand Naval plaque as it has the Silver Ferns on it but to my knowledge the NZ Navy never had submarines of their own. I take it then that this plaque was from an anti-submarine unit.
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At Molloy's MEGA ANTIQUES CENTRE, Takapuna, Auckland, New Zealand
Specialists in Pacific Islands Items, Victoriana, And a Fascinating Range of General Collectibles