See if you can pull the bullet of one cartridge. You will be able to tell immediately if the brass case has been fired. Nobody will try to scam you by using new and expensive unfired brass.
Fired cartridge cases for semiauto pistol cartridges almost always have an ejector ding somewhere on or near the rim. There are usually some kinds of sizing marks on the brass. Seated primers are often a giveaway, especially if the ammo is loaded in quantity on a progressive press. The depths tend to be inconsistent with a slight crush fit. How the bullet is crimped is also important. The bullet will often be slightly canted in the case, with the base bulging slightly at one side of the case but not the other. Also, the factories often use excessive crimp but their crimp will not remove brass shavings from the case mouth.
If you know what to look for, you can almost always detect the handloads. The way I see it, somebody who is trying to scam you will not take the time and attention to detail required to assemble ammo that can pass for factory loaded.
Dave Sinko