Oh, I get what you're saying. You want to know which string of numbers is the actual part number, right?
Most of the chips I have and use start with a pair of letters, such as LM, SN, CD, NE, etc. and are followed by a few numbers. For example, I have a CD4040, which is a binary counter. Other examples would be the LM339 (quad comparator), SN7404 (inverter), LM556 (dual timer), etc. In my experience, the actual part number is most often the first set of characters shown.
Does this help?
Der Strom