I can't really help you with the model. Eddy Merckx bikes were and still are a little out of my price range so I did not pay much attention to them. The Merckx are all designed to be high performance machines from what I have seen. Anyway, your bike is late 1980's and most bikes from that era had the serial number either stamped on the bottom of the BB or on the left side of the seat tube right above the BB. I would say that it was one of thier lower grade bikes judging by what looks to be Shimano 600 components. It feels strange to say that a bike that had Shimano 600 components is a low end bike, but that is only because most of the Eddy Merckx bikes came with Dura Ace components.