Lots of info here to digest and sort through.
First off, I don't know anything about the title, paperwork or registration process for a foreign country. I live in the United States and most places require a title in order to transfer ownership. Some states are more strict than others, but over the past 5 years or so, it's become increasingly difficult and expensive to properly title a motorcycle that doesn't already have that paperwork. I think that most guys on this forum are Commando guys, and by the 70's, I think that titles and registration information was much more common to hold on to. All the early 60's and all of the 1950's Nortons that I've come across have had issues with no title, missing title etc etc. But if there's a will, there's a way. If you love that bike, buy it, and deal with getting it properly titled and registered. If you don't want to deal with the hassle, then maybe it's just not worth it to you. Everyone is different with how much they want to put up with.
In regards to the Norton in the photos, it's definitely a 50's wideline featherbed. I believe 1959 was the last year of the wideline frame for Norton road bikes. Perhaps some were still made and sold in 1960, but after that, the slimline frame was ushered in.
In regards to the motor, I highly doubt that it's a 650. The head is definitely NOT a 650 head. But after all these years, who knows what's really inside. The bike was obviously done up as a cafe racer, so who knows what else was modified with the motor.
It's the same as anything. If you love the bike, then get it. If all the hassle sounds like too much work, then don't bother.
To me, I'd just buy because I love it. Getting the paperwork sorted out would be well worth the end result of ripping around the streets on such a cool period machine. And again, the price in my eyes is cheap. Anyone trying to build that same bike would be way over that cost. So unless the motor is blown and the frame is bent, then it's a good deal.
It's a labor of love with these bikes, and they require more work and attention than a Commando normally would. But "shit gets fixed" as they say.
Have you gone and seen the bike in person? I'd never buy a Norton without seeing it in person, unless it was being sold to me by a trusted source. But if you can go look at it and it's in good shape, then by all means, go for. I will say that the old Dominators are more difficult to deal with in regards to finding parts etc. Definitely more so than a Commando. So if this is your first introduction to Norton motorcycles, then you're definitely jumping into the deep end. But I'm all for that.
Hell, I just wish that Norton was for sale in my town.