A couple of weeks ago I got a very nice spanner wrench from SK Grimes to use on a bunch of lenses I have lying around. One was a 135mm Schneider Radionar for one of my Certo 9x12 cameras. The front elements are air spaced and full of haze, so, I thought, why not remove the retaining ring, clean the haze off and then I'll have a great and usable lens.
Sounded like a plan until I completely stripped the indents on the retaining ring and managed to jam it completely about halfway out. So even though the glass on the lens is fine it is now worthless unless I can find a way to get the ring off, but paying someone to do it will cost more than the lens is worth. Live and learn. Ouch.