Ledhead, the HIN wil ltell you year of build and that should ID whether this is a DS II or DS III, but if the boat is a 1984 or older, it is a safe bet that she is a DS II, if 1986 or newer, she is a DS III (1985 could be either, the DS III was phased in during that year apparently).
Basically, the last 2 Numbers in hte HIN will be the last 2 digits of the model year (ie: 84 will be a 1984) if there is a letter at the end of the HIN (or 2 letters on some) that is a month code. My HIN is XDY10201M79E-D, Which translates to a 1979 Model (M79), E is the code for a build month os December (A = August, B = September, etc. Model years ran Aug to July, and the 1979 Model year ran Aug 1978 to July 1979), A Day Sailer with a Class# of less than 10000 will have the D right after the XDY, but later boats it may be like mine, since O'DAY ran out of room in the 12-digit HIN.
Anyway, if you could post the HIN from your boat we can better determine the age and whether she is a DS II or DS III. A picture alone will answer the DS II vs DS III question for me.