What hole is this?

So, a while back (long while actually) I purchased a Graflex lens board for my Crown. This was supposed to have a Copal 0 hole in it. The board showed up and I put it on a shelf. Too much stuff going on to deal with it at the time.

Today I finally got around to trying to mount my lens on the board and found the hole was WAY too big. Upon measuring I found it to be a shade over 37mm. 37.3 to be exact. This doesn't match to any Copal or Compur size I can find and is close but a little undersized for a Compound Dagor at 38mm. I'm thinking though that maybe its close enough to fit. No experience with the Compound Dagor.

Is there a 37mm shutter size I'm missing or do you think this was probably meant to be for a Compound Dagor?

Not sure I mind this really. Whatever it was meant for a Dagor will fit, albeit maybe with a quick dose of Dremel tool. An old lens would be fun to play with.

Check this list of hitter dimensions out:

https://sizes.com/tools/shutter_photo.htm

I have no idea about the accuracy of the data but it's a very nice collection of information. Maybe your hole is there.

Anytime you see a Graflex/Graphic lens board listed as a Copal size hole the person listing it likely does not know what they are talking about (eyeball jister). Some Prontor and Compur sizes were adopted as Copal sizes.
A Wollensak #2 Betax, Rapax, Graphex all have a 1.325 diameter mount with a 40 tpi thread pitch. 1.325=33.655mm; 37.3mm=1.4685 inch. Mount rings usually have a edge that fits into the board to protece the shutters threads.
Lens found in a #2 Wollensak shutter are 127mm Optar/Raptar and Ektar, 135mm Optar/Raptar, 202mm telephoto/203 telephoto Optar/Raptar and earlier versions and older Wollensak lens.
#0 Copal, Prontor Press, Compur, Seiko use a 32.5mm mount; #1 Copal, Compur, Seiko use a 39mm mount.

SK Grimes has a list of the various Copal sizes on their site.