To be fair, by the time a car gets to this age bills and MoTs will tell you more about it than a stamped up service book so make an hour or so to go over the bills and see what has (and hasn't been done). Is the history complete? Has it been restored? Where has it been serviced? With such low mileage the chances are it's been pampered - but a car that's spend much of its life sitting around can also cause problems with seized components etc. As far as values go, S2 XJ6s don't quite attract the same level of attention as a Mk2 or E-type. A really good one at a dealer would be about £10k while a solid example for sale privately could be about £6k. One that's got an MoT but is very much a rolling restoration would be about £4k. However, in this case expect the low-mileage to bump the price up. Whatever you do, make sure you do your homework and use the auction's viewing day to thoroughly check the car over. If you're not comfortable take a technically minded mate along or see if the club can help with the inspection. Is this the first one you've seen? Always worth trying to see as many as possible so you have something to compare it too.