I took a quick poll of my stash, the "K" appears to be later GM production, as it matches the 2 NOS versions I have. Original production bottles appear to be marked on the bottom only, a "C", at least two different sizes, 1 marked "D F" or "P F", one marked on the side with a "BP" (which was on my '68). I can vouch for one of the "C" bottles (from my X77 since '73"), the other was on my Z11 (from '94, looks to be the same age as the X77's bottle). I can't account for the '68 bottle past '96, the NOS versions have been in my inventory since the '80's. My best estimation is likely several vendors, like we've seen a lot of peripheral (non-GM produced) parts.
Bad lighting in the garage - I apologize for the images.
Regards,
Steve