SPRON 100 is the basic alloy of Cobalt, Nickel, Iron, Chromium, and other metals.
SPRON 510 is used by many modern midrange and higher Seiko movements. It is an alloy of Cobalt, Nickel, Chromium, Molybdenum and other metals.
SPRON 610 is a more advanced alloy, used in Seiko's [Spring Drive]] and Grand Seiko Mechanical movements with 72 hour power reserve.