The Velo Retro timeline page is the best guide I've found for dating Cinelli frames. Based on it, your appears to be very early 1970s, but you can draw your own conclusions.

Serial numbers are no help at all in dating Cinellis up to at least when the Columbos bought Cinelli (1978, if memory serves). I have two mid-1960s SCs, identical geometry. Except for the color, nothing to distinguish them, and they cannot have been built more than two years apart. One is serial # 14xx, the other 85xx. I/m quite certain Cinelli did not build 7,000 frames in that time. Also, I had a 1972ish SC that is serial #15xx. Go figure.