Merckx founded his bile company in 1980. It was based just outside Brussels and the steel frames were all built on site by a tream of frame-builders. Merckx himself was very hands on in terms of frame design, choice of tubing etc. For example, the MXL tubeset was based on Columbus Max but made to Merckx’s specifications. The result is that Merckx bikes have a reputation for being very good to ruse. This along with the Merckx name means they sell at a premium.
Now the bikes that Merckx raced is a whole different story

Too simplify his earlier bikes were Belgian made, Kessels and Terryn (built by a number of individual builders) and then Italian Colnago and DE Rosa. To add to the confusion bikes from one team we’re tesprayed and used later, for example Molteni bikes from various makers resprayed for the Fiat team .