Hi Paul...
Going from this:
Live to Neutral - 234
Neutral to Earth - 282
Earth to Live - 391
Neutral to a clean, exposed piece of the metalwork of the genhead itself - 282
Live to a clean, exposed piece of the metalwork of the genhead itself - 104
Earth to a clean, exposed piece of the metalwork of the genhead itself - 0
I would say there is a possibility that the unit has been wired with the actual Neutral bonded to the Earth of the machine, not an uncommon practice and still done today in lightning prone areas.
So, if we assume that neutral and earth are the same here -
1) Your existing "Live" you measured would be a 240V output, it's a little high, 20% high, but there might be an adjustment to lower it.
2)The "Neutral" you measured would actually be a 110V output, a little low, but usable
3)Going by what I have seen in the past with "adjustments" being made, probably this unit was used in a 110V role... the output was a bit low, an adjustment was made, nothing changed(on that 110V output anyway) and the adjustment wasn't returned to previous position/setting...hence the 280v output on the 240V line...It wasn't used at the time, so why bother...
Right - Where to now? - Look for someone who can confirm this and poke around inside the thing... It's not advisable to push 280V to a 240V system - things could get a tad toasty.... or, take a chance and load the 280V line a bit (Neutral and Earth would be the Chassis of the unit, the Live would be what you had measured as a "Neutral" previously... See if the voltage stabilizes at around the 220-240 mark.... If your meter has a frequency measurement, see what the actual frequency of the output is, sometimes running the genhead a little too fast causes problems in interesting ways...(particularly with RMS voltage measurement on cheaper voltmeters)...
Long and the short of it is that its not safely saleable as is, not safely usable as is, its stuffed, if the smoke escapes while paying school fees, nothing lost! If it works to spec when you are finished - it a WIN!
Cheers
Ed
Edit: A bit of an afterthought.... Simple and easy... Put a good old 60W incandescent light bulb between your existing Earth/Neutral and fire it up with nothing else connected... If the bulb lights up, problem, measure the voltage... if not, measure from earth to neutral anyway with it connected... come back to us with your reading....