Back in the old days when racetracks still had backstretches, mixed sales were generally reserved for cheap racehorses that had issues. I bought my very first horse at the Blooded Horse Sales Company Winter Mixed Speed Sale. Well, Jake Spinner did not have speed, but he was certainly mixed, since he couldn't decide if he was a trotter or a pacer. If a horse was good, you could sell him to another horseman. Mixed sales were for weanlings and broodmares, maybe for stallion breedings. You stayed away from the racehorses, because they all had holes.