The subject of pouch rings brings to mind that laser cutters can cut
out very accurate parts from most materials that will burn or vaporize
with heat from the laser beam.  With the right program design, the
laser could engrave the two slots part way through, then cut out the
part.

Another (and probably the original approach) would be to stamp them
out with a steel rule die.  Steel rule die suppliers have tubular
punches available in many diameters.  Most of these tubular punches are
available with the cutting edge on the outside, inside, or centered.
Since the early 1980s steel rule die boards have been cut using
powerful carbon dioxide (CO2) lasers.

Bill Klinger