I sometimes I have my moments of doubting the sizing on the IDIC. It is a surprisingly big piece in person, and sometimes I worry that we oversized it. On casual visual inspection on the screen caps, it looks smaller than all of the empirical evidence tells us was the actual size.
For example, I was recently at Maggie Schpak’s workshop and she had taken a crack at a prototype for the pin before eventually turning the job down. I believe she sized it just intuitively by eye (rather than relative to the known sizes of insignia and braiding) and ended up with a size markedly smaller than ours:
But it’s nice to know that @pielock373 (who has had a ton of experience sizing TOS objects from screen caps) arrived at his sizing using totally independent methods from my own and we ended up with approximately identically sized pieces.
Here also is @JoeB modeling our pin with a Season 3 uniform (bear in mind that Joe is a smaller guy than Leonard Nimoy was by a fair margin).
Looking at the various pieces of empirical research (dress uniform braiding and Season 3 Theiss insignia patterns, all discussed in posts above), I also suspect that there were two IDICs made (a pendant and a pin) and that the pendant version is slightly smaller than the pin was.
I didn’t have a chance to take a pic of the pin on a dress uniform yet next to the braiding, but I’m working on that and believe that this will confirm the current consensus sizing.
So the Rodd.com version is basically a hybrid pin/pendant, but sized to the original pin (i.e., the slightly larger size) since I figure that is the more common way that this will be worn. I’m sure we may be off by a mm here or there, but overall I think we’ve gotten as close as humanly possible using the best pieces of objective evidence available.