Were there different variations in the OG 6P?

I just received my 3rd OG 6P. I noticed that the threads and inside the body tube is black like the FM bodies. I dont think its a fake the knurreling is exactly like my other OG 6Ps. I thought I knew my Surefire stuff, didnt know they came like this. Another thing I noticed is the tailcap knurreling is very rough and it has a protruding tailcap button and is not smooth like my other ones. I wanted to see if someone could chime in and break it down and tell me more. Hopefuly Size15s comes though. Thanks in advance. Excuse the crappy cell phone photo didnt want to bust out with my camera.

What is "OG"?

And more photos would be helpful please.

SureFire's 6P has evolved a lot over the years with tweaks here and there - give this a try, give that a try.
The threads are for mechanical rather than electrical contact (that's the rear-face of the body) so the threads can be chem-filmed or anodised it... No bother.

Does OG mean original style or something?

Curiously, I pulled apart 9 old style SFs, including 6Ps, 9Ps, and 6Zs. None had andonizing under where the tailcap sits.

Small statistical sample I know, but just my .02.

I believe "OG" means "Original Ganster" - referring to an "old" model 6P.