Engraving with the cheap 30 degree engraving bits (.2 mm point) available at Amazon - very cheap. Using V-Carve tool path, engraving at .003" per pass, and setting the flat bottom at .01" total DOC at 40-50" IPM. Each coin takes about an hour per side but I “walk away” and let it run. Then, they coins are sanded with 100, 400 then 2000. Then, buff on buffing wheel. Then, cleaned in paint thinner, then soap and water. Then, soaked in brass darkening solution. Then, lightly sanded with 2000 so the recesses stay stained.