I think late '90s is a good guess: the earlier Cinelli investment cast crown (not the classic full-sloping crown, but a later version) with similar internal plugs for the forkblades has wider clearances, less "aero" and dates from the late '80s to early '90s. This looks like it needs the "D" shaped blades, so that could help you with dates...
There's a Chinese made crown that's a very close (but cheap) copy to this, and probably didn't come on the market before 2000.