First appearance (unnamed): last panel of story in
Wonder Woman #179 (November-December 1968)
The story, written by Denny O'Neil, was the beginning of Diana's non-Wonder Woman adventures and also had the non-powered Diana being trained by I Ching.
Tim Trench would be more formally introduced in the following issue (#180) and worked with Diana and I Ching in their battles with Dr. Cyber.
In addition to his intial appearances in Wonder Woman, Tim Trench also had a couple of back-up features that appeared in Detective Comics in 1976.
He rated a Who's Who entry in
Who's Who: The Definitive Directory of the DC Universe Vol. XXIV (February 1987)