Like W.A.B. said, if its 1" then its pre 96. Also, if its got 990 on it (assuming they are factory fitted ones and not a home job) then the frame will be a mk3 Holmes, the last of the 1" ones.
Hard to put a date on it cos the mk3s were the longest running of the three 1" Holmes frames. If you give me the frame number I can get an idea if it was an early or a late mk3 frame.