I am glad it worked Willem! Here is a link to a web page that has tinkering information for the Argus C3 : C3 Information

It has an exploded view drawing of the lens that may be of some help.

The WD-40 is good stuff, as long as a small amount is used. I used to repair music synthesizers, keyboards and guitar amps. Sometimes I would get one in that was soaked with the stuff, shorting out the electronics.

Good Luck,
John