Koenig's waistcoat is only seen at the start of The Metamorph. Possibly his red jacket wasn't finished in time for that start of the episode, and a substitute was required. It's not very impressive on screen, but the actual item reveals some nice design details.
This is the waistcoat on display, with Koenig's original year 2 uniform, at the Alpha 2014 convention. The belt is also original, but the commlock is a replica. The waist coat is made of the same wool material as the uniform, with similar black stitching patterns, in a lozenge-shape above the pockets, and around the arms. On screen and in photos it appears much paler than the actual beige colour.
Contents copyright Martin Willey. Thanks to Andrew Frampton.