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
Thanks for the clarification. No rifling so likely 753.