What happened to the "Commodore" Rank?

[CorporalCaptain]

But during TOS, we did see a lieutenant j.g. Joe Tormolen with one broken stripe on his sleeves.
http://tos.trekcore.com/hd/albums/1x04hd/thenakedtimehd0230.jpg

It was also referenced in the original "Star Fleet Technical Manual" published around '75.

No, lieutenant (junior grade) was definitely not referenced in the original Star Fleet Technical Manual. I have my first edition copy "Stardate 7511.01" right here.

 

[J.T.B.]

No, lieutenant (junior grade) was definitely not referenced in the original Star Fleet Technical Manual. I have my first edition copy "Stardate 7511.01" right here.

Right, and the commodore stripes in the TM were not like what was seen on the show.

 

[Timo]

Just for fun, here's another potential Lt(j.g.), from "The Cage"...

http://tos.trekcore.com/hd/albums/1x00hd/thecagehd0076.jpg

Yeah, yeah, a different rank indicator system... Perhaps. Perhaps not.

Timo Saloniemi

 

[Mysterion]

^^^^
FWIW, Memory Alpha says that insignia is for a Chief Petty Officer: http://en.memory-alpha.org/wiki/File:Cage_chief.png

And they idenitify that fellow in the picture as CPO Garison: http://en.memory-alpha.org/wiki/Garison

 

[Timo]

...But the episode itself doesn't identify the character or his rank. Except perhaps in the end credits, but those aren't part of the Star Trek universe (and we don't really have to think that Kirk was in every episode replaced by an impostor named William Shatner, or that Uhura in fact spelled her name with three u's).

I mean, yeah, writer intention and all that. But we have now seen samples of Starfleet insignia from before and after the TOS pilots, and the system seems unchanged and continuous. Which rather supports the idea that this guy here was a Lt(jg), that Kirk in "Where No Man" was a Commander by rank, and that young Pike, doing a milk run with half a crew, was a mere Lt.

Timo Saloniemi