Help: Seiko shutter hole diameter for lensboard fujinon 250 f/6.7

[pepeguitarra]

It was still WS in the Copal shutter model.

. Interesting, live and learn. I tried to put my WS in a Copal 1 and did not fit. My WS is couple of millimeters wider to fit. I guess they made several types. According to the D.O. Industries, it is possible that the latest version (after return) could have been placed in a Copal 1.

Here is a copy of the the W only:

[reddesert]

I happened to find a Fujinon lens in one of these Seiko shutters that looks like a #1 but isn't, and I took some measurements, in the hope that it helps future perplexed people.

The lens is a Fujinon-WS 210/5.6 (older kind with inside writing), not the 250/6.7, and it's in a Seiko shutter that is the same body diameter as a Copal #1, but both the mount threads and the lens threads are different. It had no retaining ring, so this could have been a PITA, but turns out the mount thread is M46x0.75, which is the same size as a 46mm filter. So I got a 49->46mm step-down ring to make a retaining ring. This screws right on, but is too deep to clear the rear element, so I'll have to file it down a little. I'm sure skgrimes.com could make a true retaining ring for this size.

Dimensions comparing Seiko (measured) to Copal #1 (from skgrimes table):

Dimension	(Fuji)Seiko	Copal #1
front thread	M42-0.75	M40-0.75
back thread	M42-0.75	M36-0.75
thickness	~21.8 mm	20 mm
front to shutter	~12.2 mm	10.75 mm
mount thread	M46-0.75	M39-0.75
lensboard hole	~48 mm or larger	41.6 mm
iris diam	30 mm	30 mm
body diameter	73 mm	73 mm

Here's a pair of photos where I compare it (left) to a Nikkor 210/5.6 in a standard Copal #1 shutter (right). The photos have some distortion, but you can see how the Fuji lens has larger elements that fit into the larger threads of the Seiko shutter.