When they want to take a coin from your case and show another dealer before purchase.

Frankly, I hate these clods. I have good lighting and nice coins at my table.

Once I was in the middle of a fantastic world currency deal. The buyer was buying almost every note he looked at but would look it up in the catalog before he decided to buy. I was keeping a tally sheet and the profit on everyone of them was 50-100% and the show had been slow for everything else. I had already run off another guy trying to but into it with some world currency to sell (as rare as the buyer but probably looking to steal my buyer). He had come by twice trying to show me his stuff and the second time I simply ignored him.

Then this bird comes up asking a price on a silver commem in the other case. I quote it to him and he asks to take it over to another dealers table for an opinion. I tell him I don't allow that (or allow unpaid items to leave my table). Of course he would have to come up at this time in the middle of a high profit deal. He questions my policy and I tell him "Because thats what I expect." He then leaves.

Finally the world currency deal closed and I did nicely. The commem guy comes up with his dealer friend and they want to look at the coin. The dealer asks a price and wants to know what bid is. I repeat the price I quoted and then say "I don't do wholesale." They start to leave and the dealer tries to get a little smart a and say "thats too much" and I tell him "well go find one."