Type 99 Safety Knob

[Doco overboard]

I re-found this safety knob in a parts drawer with a firing pin/last ditch bolt.
Because I have never seen very many with this type of knurling on the palm surface, I was wondering if anyone would care to provide any additional info on it.
I seem to remember long ago seeing others of it's type but couldn't pull up any specifics, transitional to the more crude types but cannot remember.

Thanks for any info- Brian

[bob q]

From a Nagoya series 6 or 7 .

[Doco overboard]

From a Nagoya series 6 or 7 .

Got it . Thanks for the information.