~~~ who can pretty much date a Mother-of-Pearl chip by studying the technique of engraving where a hammer and gravers (chisels) were used compared to more recent methods; including depth of the gouge and even the angle of the vertical walls to allow better reflective visibility under candle-lit tables... and bid accordingly... and a lot more.

Here are two pieces known to be engraved by a woman (unknown to me) on the north coast of France which has her distinct numeral 7 (there are other numerals unknown to me)... with another unusual feature on a higher denomination I have not noticed on any other French plaque and, which very well be only on her art.