Could it be something like this?
Pearled border or
granitura:
MEDALLIC TECHNIQUE 27
The surfaces having been carefully polished, the positions of the
pearled border or granitura and of the inscription were marked on
them with compasses. The medallist could then cut with a grave
direct into the metal, guiding himself by his models. The letters
were also cut with gravers or burins. Some medallists used the gem-
cutter's wheel for engraving the dies. Cellini himself, however, for
his medals of Clement VII, employed puncheons or madri, 1 as for
his coins. That is to say, for the portrait-head, and for various
details, Cellini carved steel punches in relief ; these were driven into
the die, which had been softened in the fire, and left impressions in
reverse. Similarly he had an alphabet of punches for the inscrip-
tions, and a punch with dots or pearls to make the pearled border
or granitura.
https://books.google.nl/books?id=UNAMAwAAQBAJ&pg=PA27&lpg=PA...