Unfortunately, one of the plates had a defect.  When I washed the plates before using them, I felt a surprisingly large bump or burr sticking up on the top of one of the plates.  I picked at with my nail thinking it might come off, but it was part of the plate.  The other plates were fine, and amazingly seemed to stack perfectly with the 3 remaining plates from a set I bought something like 40 years ago.  Always liked these plates.  I was not thrilled with the defect, but didn't want to bother with a return. 5 plates instead of 6 for the price I paid was not terrible.  I found another use for the defective plate.