What's Chekov wearing around his neck there?
Chekov (like Kirk, Spock, and Uhura) wear their dress uniforms when they finally meet the Klingon Kitumba. As part of Lieutenant Chekov's dress uniform as Chief of Security, he wears a ceremonial Bosun's Whistle (short for Boatswain's Whistle).
Wikipedia says this about the Bosun's Whistle (also called a Bosun's Pipe or Bosun's Call):
A boatswain's call or boatswain's pipe (or bosun's whistle) is a pipe
that is made of a tube (called the gun), that directs air over a
grape-sized metal sphere (called the buoy) with a hole cut in the top.
The player opens and closes the hand over the hole to change the pitch.
They were used because their high shrill sound would cut through the noise on deck--and the noise of the weather and the surf. Nowadays, they are used mostly for ceremonial functions:

This high-pitched whistle is what you hear on the overhead paging system onboard starships.
At any rate, it appears they have mostly ceremonial functions on starships, too: security officer Lieutenant (well, Kirk calls him "Lieutenent" but the gentleman is wearing a Lieutenant Commander's dress uniform--for those of you who know how to read the braid on the dress uniforms) Dickerson wears one as part of his dress uniform (along with his ceremonial white phaser belt)--and he even pipes President Lincoln aboard in "The Savage Curtain." You can see it around Dickerson's neck here, dangling from a woven white lanyard:

And here he is blowing it as Lincoln arrives via the transporter:

Here is my bosun's whistle--identical to Lieutenant Dickerson's.



It's hard to find the proper style whistle with the proper style lanyard. (I actually had to get two different kinds of whistles and move the right style of whistle over to the right style of lanyard. Grrrr.) I think I still need to wash and bleach the lanyards; they are still new-cotton off-white and a bit stiff and not yet soft, white, and supple. From a strict naval standpoint, the lanyard itself has many specific requriements. You can read a bit about the lanyards here:
http://home.earthlink.net/~bosun-m8/index.html
So many details to tend to....
I also got two. (Better safe than sorry.) Lastly, I had them engraved: U.S.S. Enterprise on one side and NCC-1701 on the other side. (No, I have no idea if the actual Star Trek props were actually engraved in any way. It's hard to tell from the DVD screen grabs, but it doesn't look like they were; why would anyone have bothered before a High Definition era?)


Somewhere I think I have a shot of the landing party with their specail white dress uniform weapons belts. I'll see if I can find it.
As always, let me know if you have any questions or comments.
Pictures are at:
http://www.flickr.com/photos/10901121@N06/sets/72157604451565282/show/