Date Colnago frame

I've seen earlier posts in which people were able to find the date of a
Colnago frame from its serial number. I would very much appreciate it
if someone could help me out in this way! My frame has serial number
U549, stamped on the right rear dropout. (The dropouts are Colnago
branded by the way.) I would be interested to know the model of this
frame as well, as there are no decals.

Thanks in advance,
Sean Garner

If she's anything like her sister...