Multiple realities(covers information from several alternate timelines)
Gary Speckman was a Starfleet officer in the 24th century.
In 2353, he was listed as a Starfleet Operational Support Services officer on a directory placard at Starbase 32, Maxia sector. His office was located in room #45254. (TNG: "Violations", directory)
In 2371, he was listed as a Science Ops officer on the dedication plaque of the USS Voyager. (VOY: "Caretaker", dedication plaque)
In an unknown, alternate future timeframe, he was listed as an Engineering Division officer on the dedication plaque of the USS Pasteur. (TNG: "All Good Things..." dedication plaque)
This character was only mentioned in writing.