I'm not a marque expert, have seen very few Helyett Speciale bikes and none from the 60s, and I don't have period catalogues. So I can only judge what I see : a bike that looks totally original, that hasn't been touched for many years. The patina on all the parts is coherent. One of the reasons I don't clean bikes up too much to sell is so you can see missing parts haven't been replaced or a frame cobbled together out of spares.
The visible steel corrosion will polish straight off on a polishing wheel or even with a cloth and some Autosol and the bike will look when cleaned as good as I personally would ever expect from a bike of this period.
The parts seem to be all from the same era, those that I can date precisely give the same year : 1963. The others to my knowledge are coherent with this date.
So my guess is that the bike is as it left the factory, but it is only a guess.
QRs are maybe not Campagnolo, I didn't check under the white covers. Steel cranks were sometimes a choice with powerful riders.
Norris, with Juy 543 RD and Stronglight 57, your bike must be earlier than mine, say c.1958?
I think probably we're making the mistake of judging my bike by comparison with earlier models of the Helyett Speciale, from the 50s.
To me it is nice bike with nice paint and nice parts, take off the brakes that are worth 800 USD and I'm only asking 700 USD. I'm sure the parts hackers out there would have had the brakes off and replaced them with cheaper Mafacs...