How to make a 12/265mm from a Symmar 5.6/150mm

[brooy]

I'm using a Schneider-Kreuznach Symmar 5.6/150mm on my Graflex Century Graphic. It's mounted in a Synchro-Compur shutter, on a lens board. Works well (glass focusing of course, not using the rangefinder).
The design of this lens allows, by unscrewing a part of it, to create a 12/265mm.
My question is, how would I do that? Should I (try to) unscrew the back part, or the front part, or...?
Any help appreciated!

 

[jeanba3000]

If you want to look for more infos, it is called a Symmar Convertible, and it is the front bloc that has to be removed to get the longer focal length.

 

[brooy]

I have succeeded in removing the front element. It's easy, after all: just take the lens (in shutter and lens board), hold the black back element and turn the shiny front element anti-clockwise. After a few turns it will come off.

Thanks for the help.