Given that your location means you could have some talented welders fixing all-sorts of things, it isn't unlikely that the head stock was replaced at some point in the past. Supposedly, since you've had that for so-long there, it won't be a problem. If you decided to re-locate to another country, I wouldn't want to try answering those questions, should some officer question the VIN and etc.
One of the pics you included, it appears there is what looks like bare bronze brazing showing, in a spot. Paint has issues adhering to bronze brazing. If you carefully-inspect the welds/brazing there are there any-other spots like that?
Bikes do not have hidden VIN #'s like cars do. USA cars have used concealed serial #s'/VINS since before WW II to allow LEO"s to determine if a car has matching #'s.