This is the tunic worn by Alexander Siddig, as Dr. Julian Bashir, in the Star Trek: Deep Space Nine episode 'You Are cordially Invited' (Season 6, episode 7) while he was undergoing the four day Klingon Kal'Hyah ritual in preparation for the wedding ceremony of Worf and Jadzia Dax.
The original It's A Wrap! auction (and COA) description erroneously states that this was from the episode 'Dr. Bashir, I Presume'. It was sold in combination with another tunic worn by Dr. Bashir's mother.
Additionally, this costume was created and used during the time period when both DS9 and Voyager were in production and the costuming department mistakenly used a 'Voyager' tag though they got the actor's name correct.
Screen-caps are included for reference.
UPDATE: As it turns out this tunic showed up one more time on the good doctor - during another very entertaining DS9 episode, 'Badda-Bing, Badda-Bang':
