Based on some experience with the originals of some of these items, I would have to say that both Alexx and Casanova are having their parts pantographed in the here-and-now.
The stem with the Colnago sig on it, in particular, is not correct. The signature is too big, and the script is not shaped right. It's a pro job, just not original.
The De Rosa stuff seems obviously reproduced. For one thing, I have a hard time believing that Gran Sport stuff would have been panto'd, and I've never seen those patterns on any original De Rosa panto'd stuff, from any set of years. They look recent to me. Nice, but recent.
I've written to Casanova about his parts and their provenance and I found his answers mildly evasive.
Doesn't mean I wouldn't buy some of them. Some of the stuff looks plausibly period-correct, and sometimes that'll float my personal boat. Most of the time though? Not interested. The stuff from the period has the mojo...anything else? Probably doesn't. But, of course, it all depends on who's looking.