Case never made the 25 pattern in pearl in the early days (at least up to the mid 1980s). Case made a lot of SFOs starting in the late 80s and then in the 90s expanded their offerings considerably. They made no standard production pearl handled knives from about 1983 on, then they reintroduced pearl handled knives as standard catalog product in 1995-1996. I have the catalogs from 1995 to 2000, and the 25 pattern is not shown in pearl in these catalogs.
That would narrow it down a bit - the pearl 25 was evidently introduced some time 2001 or later. I do not have the catalogs from 2001 to the present, so I can't tell you what years it was made. Case in the last 20 years has made a mind boggling number of limited runs, special orders, etc. The OP may have to contact Case directly to find out the answer.
