The fork is 1991. The frame is 1990 I'm sure. In 1991, the sm700 has the same color, but the logo "cannondale" was written on the diagonal tube (like the other cannondale). In the first time, until 1990, cannondale was written on the horizontal tube like yours. If the logo of the head tube is a house, it would be a 1989, but the dropouts are 90, 91, 92, 93.
For the colors, the sm was black and green in 1990 and 1991. The SM800 best of the east was red (red shred) or black and green in 1990, and green-gold or black and orange in 1991 (like your fork)
Under the BB, You have a number. gothere
for information. 1990 and 1991 sm700 were quite the same bike. On the link I give you, you have the catalogs too !
It's a 16" because it's a 3.0 level frame, not a "best of the east" with the sloping frame. In 1990; the sloping frame used U brakes on the rear. On other hand, the BB was higher(the stays were very horinzotal. The stays of yours slopes a little to the BB). Only the smallest size of the 3.0 frame was sloping.