Who's insignia was adopted after the 5 year mission for all of starfleet? Kirks delta.
Even back then, the delta was not specific to Kirk, or even to the other captains and crews of the Enterprise
. People from other starships and installations wore the symbol in episodes like "Court Martial" and "Tholian Web" and subsequently in TAS, too...
Disagree. If you look the crew in the tholisportingre sporting a similar insignia but not the same as the Delta. Its been established every ship carried its own insignia. This was a big issue among fans when trek 09 came out.