D. Gluck was a Starfleet flag officer in the 23rd century.

In 2285, they were a vice admiral at Starfleet Academy's Starfleet Training Command. They were in Receivingship. Their office, located on the second level of a building, was in room #200. Their rank, name, division or position, and office were listed on a directory placard. (Star Trek II: The Wrath of Khan, set artwork)

This character was only mentioned in writing.
This officer was named after Daniel Gluck. The placard was sold on It's A Wrap! sale and auction for US$31.99. [1]