The piece in question first appeared in the original series during Season 1's "Errand of Mercy". And they weren't called "Disruptors". They were simply called "Klingon Phasers" by Kirk, himself, no less. The props themselves, however, were modified props from an earlier episode, "A Taste of Armageddon", made from an alien weapon referred to as a "Sonic Disruptor". Here's what those original pieces looked like:
It's easy to see the origins of the Disruptor in this shot. These "Sonic Disruptors" had their fronts replaced and new details on the top were added to give us a new weapon – the Klingon Disruptor.
These props made their debut along with the Klingons themselves in "Errand of Mercy". We can see them on various character's belts and sometimes in their hands.
In one scene we can see a squad of eight Klingons marching through the frame. All have Disruptors on their belts (as they move we can see all eight) so we know that at least that many were made.
These same pistols showed up in three more episodes. Here's one in "Friday's Child":
Next, five of them showed up in "Day of the Dove":
And finally, here's some being used by the Romulans in "The Enterprise Incident":
After that, they were never seen again. Where did they go? Well, at least one went with a Desilu executive named Renshaw after shooting wrapped. We know this because his family eventually auctioned it off years later. It was in pretty bad shape because he had given it to his kids who did what kids do – they played with it! Keep in mind that back then these items had no real value. Star Trek was simply another canceled TV series that would never be heard from again and so the props were disposable in the studio's minds. Here's a shot of the Renshaw from its auction catalog:
And now we come to the auction piece which I'll simply refer to as the Comisar:
In the mid-seventies, Paramount took note that their cancelled show was doing huge business in syndication. Since Star Trek was suddenly a success, the studio guys got a bright idea – let's bring it back! And so, Star Trek: Phase II was born. While that production would feature an updated Enterprise (inside and out), it was decided to keep the design of the costumes and props, a decision that would save tons of money. To that end, Paramount rounded up anything still in storage from the original Star Trek, most of which was in the form of costumes. But a few props remained, most notably, some of the Klingon Disruptors. Since those survivors were undoubtedly in "used" condition, they were freshened up with new paint and new foil on the forward fins.
It was in the middle of pre-production of Phase II that Paramount abruptly switched directions, pulling the plug on the project in favor of making Star Trek: The Motion Picture. Phase II became a largely forgotten footnote in the history of Star Trek.
Here's the catalog description:
"This wood prop was acquired from Star Trek: The Motion Picture’s property master Richard Rubin, who received it and other materials from Star Trek: The Original Series during pre-production on the Star Trek feature film. This and other props were refreshed by Rubin for potential use in the film, including fresh blue-grey paint, though the wood body exhibits still numerous chips and marks beneath the fresh paint indicative of use in The Original Series. Ultimately, the disruptor props from The Original Series were not utilized for filming on The Motion Picture. As a result of great care by Mr. Rubin’s family and after by the Comisar Collection, the weapon exhibits only minor signs of wear and is in excellent, production-used, vintage condition overall."
The one error in this text is the attribution to Star Trek: The Motion Picture. It's a natural mistake, however, given that all of the development for Phase II was rolled over into the production of The Motion Picture. The important take-away from this is that the piece came from the Star Trek production through prop master Dick Rubin, an idea supported by a number of other Original Series pieces that came through Mr. Rubin's hands. Again, these weren't seen as having any real value so it was not a big deal for the prop master to take them.
I want to make note of the fact that I have done a lot of research on these pieces over the years because I own another copy of Disruptor, one that Mr. Comisar had also gotten from Rubin and then sold to another collector. That story can be found here: My Klingon Disruptor.
Here's some more great shots of the auction piece (click on them for larger versions):
You can see some of the original wear and distress on these close-ups. That is to be expected from a production-used piece. In fact, I would be worried if it wasn't there. This piece matches in every way all the details that are known about the original versions. It is not often that I say I have ZERO doubts about a piece, but this is one of those times. Its details, combined with its provenance, make this a classic piece worth having in a museum, let alone a private collection. These kinds of things don't come along often and I'm sure it will find a good home.
Prop Store has other fantastic Star Trek pieces in the auction so I urge you to check those out as well. You'll find the auction details including a downloadable PDF and the on-line catalog at Prop Store's Comisar Auction. If you've always wanted a piece of Star Trek history, there's no better opportunity than now! Bidding is now open with the live auction taking place on December 1 at 10:00 am PST.
Best of luck!