This Rogue Trader-era Eldar Warlock with Force Staff was a 1990 Jes Goodwin sculpt, appearing in the 1991 Blue catalogue with credit.
Another copy:
The back of the tabs look like 1999 to me, but since it appears in the 1991 catalogue I’m suspecting it’s either 1990 or 1989…
This was one of the miniatures available from Games Workshop as a Made To Order unit in 2025.