Possible Bidding Issue

Without specifics it is difficult to offer any meaningful opinion. You said the coin was "somewhat obscure" which in itself is an opinion that may or may not be shared.

Generally, if you are working with the better known auction houses, such as Great Collections or Heritage as the first two names that come to mind, the chance that you would be shill bid is absolutely zero.

Since you don't mention the firm, that too is difficult to access.

It may also be a matter of bid leveling, as I call it. For instance, if I see a coin I like on Heritage that consistently sells for $211 with the .175 vig, I know a $180 bid will likely clinch the purchase for me. Not always, but quite often. Also, if you are getting close to a JUMP in bidding increments, that can also have an affect. If, for example, you were at $990 for your top bid and at $1000 the bid increment jumps to $100 more per bid, then some will quit bidding when it hits that plateau.

But really, without knowing considerably more than you have offered as far as the details are concerned, I'm not sure how much help can be offered.

You say it is obscure, but a five figure item so it probably isn't THAT obscure. So there could be some other specialist interested in it as well. Unless you can show that the underbidder has connections to the auction house it may just be another specialist that knows what it is worth. Even if they are connected to the auction house, check the terms of sale. Most of them allow the auction house to bid on items for their own account. Usually though withthe more ethical houses they do that by placing a max bid on the item. In that case since you also placed a max bid ahead of time it would have opened at one increment above the underbidder so there would not have been continued bidding against them. It sounds to me that you just got into a bidding battle between your book bid and a floor bidder. The fact that they stopped just below your max bid was either a coincidence or the result of someone else knowing what it was worth. Unless you have more compelling evidence I would just consider it to be normal bidding.

This is a big reason why I rarely use proxy bidding. You don't know if something shady happened in your case but your instincts tell you there could be something going on here. I will sometimes put in a relatively low ball proxy bid but usually snipe on ebay or Great Collections or use Live Auction on Heritage if I really want something and am willing to pay up a little.

Yeah, putting in your max bid ahead of time is a bit risky. Even though you can't prove anything negative went on, just having your bid "out there" ahead of time leaves a door opened.