Not my area, but I think this might help.
When James Parker and son introduced the "Pit Bull" brand, the tang stamp logo was that of two dogs fighting.
I do not know how long that branding continued, but given the eventual outcry over dogs being trained and goaded into fighting to the death, not to mention how some breeders/owners treated the dogs, i.e. termination, the activity became pretty much socially unacceptable.
The NFL Georgia Falcon QB fiasco, trial and imprisonment made things worse.
So, Parker changed the branding and went to a single non-violent standing dog logo.
I assume the originals have some kind of cult popularity and sell for more than the later, less politically incorrect ones.
Parker, in their later catalogs touted some knives as, "First Run", etc, I never bought any, so don't exactly know what those knives looked like. Were they the fighting dogs variety or was "First Run" simply a ploy to sell knives?
I don't know.
Charlie Noyes