I find the varied approach to estimates done across the different auction houses quite bemusing. There are a range of them laid out above but I had always considered that the estimate was the auction house estimate of what the hammer price would be. There are many factors in my mind which can skew this. Collectors don't have a margin in mind and are often looking for a coin that they want to add to their collection and the point of buying at auction is that they can generally get this for less than they would spend from a retail outlet. In general if a collector is interested in a coin then the dealer will normally be outbid as the higher hammer price is eroding their margin too much unless they are willing to accept a lower margin for that coin (let's face it they still want stock). This can lead to a perception that there is inflation in the market if enough collectors are bidding and driving general hammer prices upwards. Specialists might see something in a coin that the auction house does not and in this case when two specialists in a field see a coin then all bets are off when it comes to estimate. In this case the specialist will normally win leaving the general collector and dealer behind. There are times however when the coin is a specialist coin and I fail to see how the auction house could possibly place the estimate on it that they come up with. In the most recent CNG EAuction 468 there was a Probus coin that sold for 12 times estimate. It was a very rare bust type and well beyond my means but when I saw it before seeing the estimate I guessed it would reach 10 times the estimate and was left bemused when I saw what the estimate was. The estimate would have been about right for a coin of this type with a more common bust type. At this point you have to question the value of providing an estimate on such a coin as the auction house was way out. There were many coins in this auction where the coins went for many times their estimate. I suppose this comes down to how you estimate the market price for such a coin to base your auction estimate on. If this market price is completely wrong then there is little or no value in having an estimate at all.