I ran one, as per Annette's pic, about 20 years ago. Had it shipped to Spain for a while, but that didn't work out as it didn't really like 2-up work, so it came home & was sold on to a guy in Farnham.
The design detail is amazing, but I always thought the choice of engine was inappropriate for what was intended. They need looking after carefully, as the finish is poor in places, so watch for salt damage. Suspension is a tad budget too & only that single front disc sans ABS - clearly the bean counters got involved. Chassis/body parts are becoming difficult, as you would expect, given the numbers produced. I'm not sure about the tank, carb etc when it comes to E5/10 fuels, so that needs research.
If your father wants a bike to polish & admire, that won't depreciate, for the occasional sunny Sunday, then fine. If he wants something easy to ride then look elsewhere - I would have thought an Enfield 650 or the upcoming Goldstar (not that we've seen one OTR yet) might hold more appeal & be more easily managed when it comes to parts/service.