I am pretty sure it was the UK proof. that was not really a factor since I have more than a couple copies of BH in different editions and languages. The price was only about 20$ difference so that wasn't really a factor either. In the end I think it came down to the condition of the proof and the fact that it was the first On Writing proof that I stumbled across. I was not really intending to make a purchase that day so it was a spur of the moment choice, as both auctions were ending in under ten minutes. I can always find a copy of BH if I am actually shopping for one, so I am just curious as to what others would have done and what price would you guys have considered a good deal for the On Writing proof.