Originally Posted by CyclesMakaron

H C5651 - frame built spring 1991
Here is a slightly later one:
speedbicycles.ch/velo/295/eddy_merckx_motorola_hampsten_1991.html
Motorola competed in the 1991 Spring Classics
Check the tube ends visible through the BB cover, if they don't have "riflings" then your frame is built with 753