Was the Lego Wright Flyer kit, which appears to be pretty rare, for a tenner. Unfortunately the box is badly battered and it appears to be missing three out of 600-odd bits though I'm hoping it may turn out I've somehow sorted them into the wrong bags or something. One is still available from Lego, the other two are out of stock. It sells for a couple of hundred complete, I'm hoping it'll still be profitable in its current condition.
later - found all three on ebay - cost £4 or so but it's worth it to be able to offer the kit complete.