Blue plate, vintage Bauer, Los Angeles: 434,800 parts per million lead.
Tested negative with Lead Check swab (which are designed to test for lead on painted surfaces – not pottery)- Why take the risk? The only way to know is lead is leaching is to send it to a lab. Better to have lead-free dishes and not worry!
Please note: I am not saying “this particular plate will poison the people using it”! I am saying that there is no defensible reason for one of the most potent neurotoxins known to man to be in our cookware (especially at levels this high!) Period.