Necchi is, as I understand it, the mercedes benz of machines. I have one old one not in working order at the moment.
When I had narrowed down my choices (just like you) I sent the links from eBay to Billy (Lostn51) and took his advice. He's the one to ask.
I got a 1961 Atlas that looks like it is showroom perfect. Even though I intend to use it and oil and clean it myself, I felt more comfortable taking it to my trusted guy for a tune-up, so it isn't here yet, but asking Billy made me far more comfortable in my choice.
Good luck.
(You know, if you end up with several that you want, and different prices in your head, you can use AuctionSniper in a bidding group. It will bid on each one up to the price you put on it, until you get one. Then it will stop. For items like this, it's my way of not getting into a bidding war.)