Every time I go to sell a lens board, it’s like every time I go to Home Depot to buy wood: it’s never labeled. So I wind up Googling the world to figure out what size the damned hole is. Now, once and for the problem is solved.
For anyone who has the same problem as me, here is your answer:
Copal O – 34.8 mm.
Copal 1 – 41.8 mm.
Copal 3 – 65.8 mm.
What brought this up you ask? I’m selling my Linhof Tech IV on ebay, and I have lens board with it. And it’s a Copal 0.
Now you know.