There were some entry level Merckx made and I have been lucky (poor choice of word perhaps) enough to view one in the flesh, so to speak. The one I saw was a step through model and definitely had not been repainted. With that in mind, the OP's bike, even with the claw hanger, might be legit. It has been upgraded with a saddle and Campy NR transmission (1970 as near as I can tell). If the hubs are Campy, look for the two digit date code stamped on the inside face of the lock nut. If it matches, then you might assume original components have been fitted to the bike but this is not cast in stone.
What ever it is it is pretty. Depending on how much the asking price is, it might be worth having.
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"98% of the bikes I buy are projects".