It would be my assumption that the ‘V’, large and bold, was stencilled on to the firewall spar cover to distinguish, both in the Castle Bromwich factory and in the field, the MK V from the Mk II .

Equally the large ‘9’ to distinguish the Mk IX/XVI from the Mk V.

With no engine and bearer the differences are not visually obvious particularly with the overlap of RAF serial sequence.

Mark