It's my belief that the engraving is done on the metal die used to mold the chip, not directly on the finished chip itself. Even a hundred years ago, machines existed to precisely engrave geometric designs on metal. I suspect the rim design is machine created, while the monogram is engraved by hand in the center of a die. Again, not scrimshawed on the clay chip, but cut into metal by the engraver.

What I don't know is how the hand engraved dies were "reversed" so that the monogram and rim design end up incuse, not raised on the finished product. If this is done mechanically, then all the dies could be made from one original and all the hand engraving should be the same on all chips... which is not the case in the "boot" chips you showed.

We need someone who was around in 1890 and made some chips [g].