A " private treaty sale" is a service whereby an auction house will broker a sale between vendor and buyer discreetly, outside the relatively public auction schedule.
After I heard about it, I sorter oozed around the barrooms pickin' up gossip and I found out that somebody wants to buy in Tara cheap at the sheriff's sale, if you can't pay the extra taxes.
No one had ever beheld the three Rubens that he possessed, his two Watteau, his Jean Goujon pulpit, and the many other treasures that he had acquired by a vast expenditure of money at public sales.