Thanks for the responses. I went out in the morning sun and put my reading glasses on and discovered more of the serial number, but it still doesn't match any information I can find online. It starts with a number not a letter: "2 1844 D." The D is faint and might be an E, but it still does not tell me the model or when it was built. I'm guessing sometime between 1980 and 1984, and I guess it is probably either a "Professional" or a "Corsa" model. The Merckx company won't respond to my emails. I'm going to try calling.