My friend owns what we consider an early "Professional".
The frame number on the bottom bracket reads
"6." ("six dot") on the left and "749" on the right.
The seat stay caps have the signature on them. The fork crown has "Merckx" engraved.
Can you date it?
There is something unusual on the underside of the lower frame tube, a marking that reads "MPS - STC 06548" (?, sorry for the bad pictures). This marking is not engraved but raised, like Braille. What is that...?
Thank you very much in advance!