AndyMcKinney
Senior HTF Member
Though it made it easy that Shatner's tunic has no delta insignia on it. Nor does the evil Kirk who beams aboard. I don't recall if if the missing insignia is explained by anyone. Maybe they left the insignia off as a way to show the evil Kirk as a mirror image and realized it wouldn't work.
If you're talking about the "normal" tunic (i.e. not the wraparound one), I'm pretty sure it was explained that this was simply a 'laundry' mistake...the insignia were always taken off when the uniforms were cleaned, then sewn back on. Apparently, Shatner's insignia didn't get sewn back on and no one caught the mistake when filming that part of the episode.