Mate, having owned a few of these, do not be put off by the miles. IMHO dukes like to be ridden, not just admired. Like most folks have said, check the paperwork (twice). I actually think its about the right money, it does come with some costly bits, mainly the monoposto. Just bear in mind it is 'only' the BP version, so a bit down on power. Also, does he have the original bits? ie wheels, pipes etc?
I looked at this one on ebay for myself and was very tempted then, only reason I did not go ahead was because it is an early gold frame (and I really wanted an S

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Where is at fella?