There is a supposedly screen used Star Trek TOS costume on eBay from "What are Little Girls Made of?". You can see it here. There was some question about the costume.
First of all, this is what was posted on October 19th by a Star Trek Prop, Costume & Auction Forum regular:
"The "WALGMO" costume (as shown in the e-Bay posting photos) does not match the one seen on Dr. Brown on-screen. Hi-Dev screen caps on Trek Core clearly show that Dr. Brown's costume had front thigh pockets on both sides. Granted, they could have been removed after production. But why? Screen caps do show what appears to be a match for those large adjustment buckles seen on the back of the costume, but the caps are dark and the details few.
As the seller IS NOT accepting returns, I would be very careful with this costume. Several questions I'd have; Does the costume show any evidence of ever having front thigh pockets? Could that costume be a repro made by Paramount for one of their many traveling Star Trek exhibits, or possibly for ST: The Experience?
Another thought; Ken Caslis did get some items from the Bill Theiss estate. Perhaps this costume was made for, but not used in "WALGMO". Theiss kept costumes from Star Trek, so it's possible that this was one of them."
In response to these exact questions, the seller posted a revision to his ad on eBay today, October 21st, to include this:
"Update: There apparently were front pockets on this outfit when it was filmed for the episode. These front pockets were subsequently removed from the costume. I can see faint stitching lines on the front of the outfit on both sides indicating where the pockets used to be sewn onto. Thanks guys for pointing this out!"
I do think the seller overstates Ken Casslis' credentials. As far as I know he sells through Profiles, and does not authenticate for them. Ken was one of the two guys who got all the Star Trek props from Paramount and sold them in Profiles for years. I do not have any information about Ken's expertise, but I would suggest James Cawley, of Star Trek: Phase II (formerly New Voyages) is a better choice as an expert. James actually worked for Bill Theiss.
This seller has two other interesting lots on eBay and I will review those tomorrow.