Vintage Kessels Merckx first generation racebike 1971 - 1973
How to identify a high-end frame?
How to identify a Kessels 3nd generation frame?

 Vintage Kessels Merckx from 1977
High-end, third generation
Made for a client for the shop of W.Benoye

Vintage Kessels Merckx Molteni bike from 1973.
Presumably mid-range: eye-lets, no hollow seatstay, no two holes in the BB?
How to identify a Kessels Eddy Merckx frame

Eddy Merckx and his Colnago frame dimensions 1970s.
With thanks to All Bikes Putte Belgium.

Vintage Kessels Merckx frame,  third generation 1977 - 1979, how to identify a high-end frame?
It is always a subject of discussion. The thread running through every story is: Kessels did not make
frames but imported them from framebuilders. Vaneenooghe in Ruiselede and Gaston Orlans in Gistel, both in West Flanders Belgium were two of the builders. 
On the photos below you can see only high-end Kessels-Merckx framesets  similar to the ones
Eddy Merckx used in different races between 1971 and 1977.

 Vintage Merckx De Rosa Fiat Tour de France 1977.
The current owner recieved confirmation from Mr Eddy Merckx about the 
authenticity of the frameset. Contact with Mr De Rosa regarding the meaning of GF+ learned that this bike
can be dated in 1977. All sizes and dimensions were measured. They proved to match perfectly with the certified bicycles of Eddy Merckx. 
Many thanks to Mr. Wynants.

Terryn Charles speaking  ...

Vintage Merckx race bike factory

 Vintage Merckx Professional racebike 1984