Merckx (like most producers) could be inconsistent with numbering etc, but I'm fairly confident given the frame details that this is an early Corsa Extra.
I've never really found anything of any quality at the Dump, but my brother in law stumbled across a lovely Freddie Grubb with a full Campagnolo group on it. The chainstay was a bit bent, but easy cold set. Good to ride again!
Daftest thing I ever did was found with me cycling back with nearly an entire bike on my shoulders (arm thru the triangle style). The bike looked cool in photos, vintage 60s Campagnolo but it had been painted black. Only when I saw up close and the headbadge did I realise it was a Saxon Twin...
We did Mont Ventoux in '22, thought we were going great guns till about 1km from the summit when a tandem casually passed us by! Great climb, but absolutely zero shade after about a third of the way up