~~~ serial-numbered chips is that they can easily be followed; especially the high-end material which has been published in price lists or numbers recorded by a seller.

There are such chips where only one is known yet, it is visible to see where that chip has traveled over the last 40-years. Also, there are some chips broadcast as being in one's collection which are actually not... Saving and comparing pricelists can be very interesting as is saving private inventories (collections) copies of chips. One such example I know of is a plaque from Spain I sold a few years ago with a serial number of '8' which has changed hands in Asia no less than six times...