Gundlach Achromatic Meniscus has a Removable iris.

[Louis Pacilla]

I discovered this late last night. My15"f6 Gundlach Achromatic Meniscus Portrait lens has a removable iris. As you can see in photos My version is the all brass early version. I,m not sure if the later black enamel version has the removable iris.
This leaves the lens at max f4 or a bit faster. This shows a good deal more diffusion w/ iris removed versus w/ iris.

I have not made any images w/ the iris removed but studied the ground glass last night. I believe this would be fantastic to shot it this way at times. Not always though and the great thing is you can simply screw the iris back on. No gaffers tape, clamps, or more involved methods needed. This makes field use w/ out iris (with extreme diffusion) easy . Just twist the iris off. The iris is a solid unit kind of like removing a cell from convertible lens.

I just wanted to share this info. I know Jim G & Jonathan B have this lens or two or three,,,,,

BTW -I could not get any of my similarly constructed diffused focus lenses iris's to screw off. I did not get to involved. If the iris did not come off w/ a fair amount of pressure when I twisted. I quit trying. Not worth the possible damage.

[goamules]

Good discovery. If you think about how they manufactured these lenses, most of the parts of most lenses come off. I've taken barrels off of several makes of Landscape meniscus for example. Sometimes they are pretty tight at first, because they weren't intended to ever be removed once manufactured. But a lens repairman would need to get the iris off your Gundlach, if it every broke.