Ever been to an estate sale where there is reloaded ammo for sale? I've gone to quite a few. Many times the heirs/spouse or auction house will combine mixed partial boxes to make full boxes for easier sales, and ease of displaying/moving. Many don't have a clue as to what they are doing, nor do they care, they just want to get rid of it. I have some reloads for revolver that were made with Lil'Gun. Not unsafe to shoot, but hard on revolvers that I need to get to and pull, just in case someone unknowingly uses them.
I sometimes buy that stuff, but I always knock out the bullets, discard the powder (who knows WHAT it is), and salvage the cases and the bullets for my own reloading. ;-)