Actually, 1983 was the last full Model year for the 25, 26 was phased in for 1984 model year (August 1983-July 1984).
There was actually one (and ONLY one?) 25' O'DAY built during the 1990's, Rudy had an O'DAY 250 that he had built, it was actually a re-named O'DAY 240, but restyled slightly. I doubt that is what this guy has for sail. Of course, the 1990's O'Day 25 listing could be a miss-print, on eBay there is a 1997 DS II listed (it is actually a 1979, so the number must have been reversed).