Would a Hurricane IIB have twelve 303 Brownings? The other photographs on the Bundesarchiv link show more of the wings and what appear to be two additional guns; I can’t ever remember seeing a twelve-gun Hurricane in a period photograph before.
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A Mk.IIB would be expected to have 12 Brownings, this was the build standard for all except fighter-bombers which only had ten because the carrier occupied the space for one of the guns. This is also true for those carrying a fuel tank in this position, it being jettisonable on the Mk.II and later. It is reported that on pure fighter examples the outer two guns in each wing were often removed to save weight and improve agility, but this was not universal and it is difficult to pin down just when and where. Not, it seems, in the UK. Or on this example.

My comment about a possible vertical on the second letter (H or K) was contingent on the first letter being an A (i.e. 213 Sq) not an N.