This costume was originally sold on eBay by It’s A Wrap! in week 89 of their Star Trek auctions. I purchased it recently from Darrin on the Trek Prop & Costume Forum.
The costume features a tunic with metallic floral print fabric and massive, flowing bell sleeves. This fits under a “vest” with a cast resin “jewel.” The costume also includes a wonderful pair of pants. The pants and vest are marked with Paramount wardrobe tags “4-3.” The accompanying hat is marked “1-20” so it was probably not originally paired with the costume. However, the metallic floral pattern on the hat band is similar to that on the tunic.
This Vulcan Priest costume was designed by Robert Fletcher for Star Trek III: The Search for Spock. It was worn by one of the Vulcans who greeted Kirk and party as they brought Spock’s body home to Vulcan.
Costumes of this style were later used for Vulcan diplomats in Star Trek VI: The Undiscovered Country and for slaves of the Intendant in Star Trek: DS9‘s “Through the Looking Glass.”