Richard, I don't know the answer. I just noticed two different numbers on the one panel. Maybe an earlier one is modified to a later number?
Another number on it has been cancelled.
Kevin 79 welded Armoured O.Ps (MkIIIw) came to N.Z., 40 of which were later sent to Tonga. Apart from my one, there is one runner here in N.Z, and two bare rebuildable hulls, that I know of.
The only other AOPs that I know of are Nigel Wards MkII here in Australia featured in Nigel Watsons 3rd book (he told me of another Australian MkII) and a late MkIIIw in France also in Nigel Watsons last book.
Your panel has a cut out in the left lower corner. I assume these panels are from the later AOPs like the French one. It IS just my assumption.
So many un answered questions.