The crystal chips were known long ago but I have never seen one.
Several years ago, Mandolin had one or more Model Ms that had them and put them up for sale at a high price. Naturally, he was flamed mercilessly because the hobby was far more likely to rain down wrath on people charging high prices back then than they are today.
Because of the brou-ha-ha, those crystals became known thereafter as "Mandolin crystals".