Is this board the same size as the early Speed Graphics (pre & Anniversary) ?
I've a Bakelite board that came with shutter, and an original unused wooden one stamped with a C (I assume for Calumet) drilled for a US shutter a touch smaller than a Copal/Compr #0,
If you can't find one I will possibly have a spare metal board, it's for Compur/Copal/Prontor #3 but had a plate mounted across it to adapt for a smaller lens at some stage, and I've literally just super-glued another undrilled aluminium panel to it about an hour ago
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Ian