How do I remove these pushbuttons?

Trying to redo a panel on a GSSL, and I'm taking everything off prior to printing the faceplate...

But I cannot figure out how these illuminated pushbuttons are to be removed!

I thought I'd desolder the connections and then undo the collar nut... but midway through, it occurred to me that the 'block' of the switch assembly is too large to pass through the hole!

From the back:


...and the front:


I'm baffled!
(I didn't build this unit, so it's come as a surprise!)

http://www.mouser.com/ds/2/307/a16_ds_csm602-32907.pdf
Page 27. I haven't used these, but I had some free time at work to do a search for illuminated pushbutton, this looks like what you have. Two retaining clips, you may be able to remove without the special tool, and without desoldering!

Thanks!

Yep, I was just returning to say that I found the clips... Actually this is not a bad design, for that very reason, now that I've got it figured out. -No special tool needed, I just pushed gently outwards with a pair of jewelers' screwdrivers and off they popped!

I think I might actually use these myself in the future. -They could possibly even be PCB mounted, but still removable, providing access holes are left in the PCB.