dating a retro colnago frame

[jax]

Hi... anyone out there can give me some indicators as to dating a colnago tecnos frame?? I believe the one I have is a 90s.
someone asked if it had a clover cut out under the bottom bracket but went on to say he didnt know what it meant anyway :roll:
any guidelines would be great....
here is a pic of my bottom bracket.
cheers.
Jax

 

[dutchie]

http://www.flickr.com/photos/heathkneller/121208918/

Maybe he means this, to my knowledge are these the older ones.