It never ceases to astound me that people don't contact the manufacturer but instead ask random strangers on the web for info. I sent an email to Colnago (in English, even though I could've written in Italian), and got a very helpful correspondence going, which in a couple of rounds got my used Colnago identified. Email info@colnago.com, attaching a photo of your bike. If you have the serial number, include it. If not, they'll be able to direct you to where to look for it. Once they have the serial number, they can tell you the model, year of manufacture, and probably even the frame size.