PSA. According to a FFL friend who does a lot of transfers, it's hard to find the blem on most of PSAs lowers, the majority would pass as new. He said during the panic, when prices were high, people got really picky and weren't accepting a ton of the stuff he was transferring, any tiny imperceptible flaw and he would have to send it back. To counter this, PSA started selling the majority of lowers as blems to avoid that even though most would've passed their QC pre Sandy hook. No idea if really true.