Hi! The Merckx 753 did not have any special markings (never), it almost always had the EMC employee symbol (in your P frame, always knocked off atypically to avoid confusion with the weakly knocked out R which always meant Reynolds 531), sometimes a number indicating the size of the frame (almost always stamped on fork tube) and serial number (from 1981 always preceded by the letter of the series: E, Z, A, B etc. - without the second series E, it existed only in the imagination of GITA employees The first series EM753 is nothing different from the normal Eddy Merckx. .. except weight (and riflings in Columbus SL / SLX tubes); the second series EM753 should have a different brake bridge (Silva "flat bottom" instead of Gipiemme "cube") and not have riflings. Your serial number may only match these two series. EM753 I do not call Grand Prix, because this name appeared in late 1988, and your frame is the breakthrough 1984/1985. P does not mean Professional, because such a model has never officially existed (and the designation P can be found on every model of the frame produced in 1984-1986: Eddy Merckx, 3-Athlete, Pro SLX, Pro 753, Corsa, Criterium). Regards - Jacek