As we know, Spyderco's design was the VERY FIRST to have a thumbhole in the blade, and a pocket clip on the handle.
And the VERY FIRST Spyderco C01 has only 2, not 3, screws (inset closer together) on the pocket clip and no lanyard hole, like mine:











As you can read from Sal's post back in '10, these were first seen at the Texas State Fair in Dallas, October 1981.
From what I've read and researched, the second variation still had no lanyard hole but had 3 screws on the pocket clip.
The 3rd variation, 3 screws on the pocket clip with finally a lanyard hole.
Footnote… the 'Evolution Set' replicated this first edition with the 2-screw clip - but the screws were set further apart, beyond the clip width.
Thanks,
Sid M.
