Just to break down what we do know so far it appears that Merckx could have ridden a 6-speed freewheel and the diamond chainstays are consistent with a Ugo DeRosa built frame. The Pista pedals are consistent with what Merckx rode at this time as is the NR group. The skewer shown on the rear wheel is 1978 or newer (a replacement by a later owner?) but the brake quick releases are the early style.

None of this is proof that Merckx rode the bike in question but it is consistent (for the most part) with what a Molteni team bike of that time period could have been. So I personally would rate it a could be! Hardly enough to spend $25,000 on. Part of my problem is that he is selling three Molteni bikes; he shows the Merckx bike with white bar tape in one photo and blue in another. It is hard to determine exactly which bike is which.