Since I’m still
in Information Mode here—yep, Bones has a pinky ring! It’s not
super easy to get a good look at it, since the camera never
particularly focuses on it, and sometimes he seems to be wearing it
with the stone turned inward to be less conspicuous. But once you
start looking for it, you’ll see it.
[ID: Three shots of McCoy; in the top left one he’s looking off to the side with his hand touching his chin, in the top right one he’s taking a drink from a glass, and in the bottom one he’s holding a futuristic-looking visor to his eyes. In all three pictures a ring is visible on his little finger.]
As far as I know he’s always got it on. He even seems to still be wearing it while he’s working on the Horta, which, I mean, that’s dedication, man.
[ID: 1. A shot of McCoy standing in a cave next to the Horta, looking down at his tricorder, showing the ring on one hand. 2. McCoy holding up his hands with the cement mixture all over them, with the shape of his ring visible underneath.]
Like I said, nobody in the main show ever mentions it, so there’s no Watsonian explanation for why he has it (though I would bet that it comes up somewhere in the EU, because everything comes up somewhere in the EU). But the real-life story behind it is quite sweet. The ring belonged to Kelley’s mom, who he was very close to, and after she died he kept the ring and wore it in memory of her. When he wanted to wear it on TOS, Roddenberry initially said no—because he didn’t want any of the cast wearing modern jewelry is the explanation I’ve heard, although Uhura’s wearing earrings all the time so, I don’t know what that’s about. Anyway, Kelley told him that if he couldn’t wear the ring he wasn’t going to be on the show, and Roddenberry wanted Kelley in the cast more than he wanted the no-jewelry rule, so he acquiesced.
It must have been pretty dang important to Kelley, because that’s pretty much the only story I’ve heard of him ever pushing for something like that (the only other instance I know of is when he and Nimoy refused to have McCoy and Spock betray Kirk as initially written in ST V, because, as they told Shatner, that is nonsense). I’ve heard stories of Shatner making demands and of Nimoy insisting on things, but no other cases of Kelley doing anything like that aside from those two. I mean, obviously, I wasn’t on set, I don’t know, but he just doesn’t seem to have been the kind of guy to make a fuss about something unless he had a really good reason to.
I would presume he wore it on his little finger either to avoid giving the impression that it was a wedding ring, or if it was a woman’s ring it just might not have fit on his ring finger. Or possibly he just did it for the Look.
Personally, I’m glad Kelley insisted, because it’s such a nice little touch of character. Roddenberry had a problem with getting so focused on making sure his characters adhered to his idea of what people in the future should be like that having them actually come off as real, relatable people tended to take second place to that. The ring is a small thing, but it’s a sign of a character that exists outside of the immediate situations we see him in. In-universe we don’t know if the ring is personally significant to McCoy or if he just likes it as an accessory, but either way, it points to a little bit of history and personality that’s not there to serve any function for the plot or to make any kind of significant point, it’s just there because people have little bits of history and personality like that.
He’s still got it in the movies, incidentally.
[ID: McCoy in Wrath of Kahn, laying on the floor with his head propped on one hand, gesturing with the other hand, showing the inner band of the ring on his finger.]
But sadly it doesn’t appear to have made it into TAS.
I am shocked, SHOCKED that a series with such IMPECCABLE attention to detail as TAS somehow missed a thing like that.
[ID: A shot from Star Trek: The Animated Series, with McCoy sitting in a chair opposite a brownhaired redshirt woman, both hands visible with no ring present.]
However, if you’ve ever noticed that McCoy is wearing a ring in the AOS movies…
[ID: A shot of McCoy in Star Trek (2009), standing next to Sulu and gesturing with one hand; on the other hand, tucked against his side, is a large silver ring.]
..it’s because Karl Urban knew what he was doing.