I have some of these, but in a different brand, and in a couple of colors. they're a 'lacquer stick' that is used to fill in the engraving done by the various New Hermes machines. after you to your burr removal, which is a must to avoid a ragged appearance, you simply rub in the letters/numbers, and carefully wipe off the excess. They will 'skin over', which keeps them from completely drying. I believe McMaster-Carr sells an equivalent product.
i've used these back in the dark ages. they're useless for serious engraving. they were originally made to change the color of engraving. if you have a need to do that, paint is far superior.