Hi,
This may not precisely address your problem, though it does involve a plate and some unusual markings.
My Opa was visiting our home. Every morning he would make oatmeal. Instead of serving it in a bowl, he would spread it on a dinner plate to cool more evenly. He would always begin by eating from the outer edges in a circular fashion, where it was coolest, until he worked his way to the center.
On this particular day, Opa noticed an usual black pattern was visible on the plate as he was eating. All the other plates from this set were an ivory glaze. When he inquired why this plate was different, I glanced over, then reported, "Oh that was the plate I burned my bra on." In one swift movement, the plate was in the garbage and my Opa was screaming I was trying to poison him.
In that era, women were allegedly burning their bras though I never saw a public demonstration. I had an old one and was curious what would happen. Once my experiment was over, I thought nothing of dropping the plate in the dishwasher. This plate was in continuous use until this little show of emotion.
Yeah, some things one should probably not admit to.
Regards,