This is a 2nd generation Checkpoint motor based on the Yokomo modified teardown as introduced at the 1/12th scale worlds 1982. Big Jim Greenemeyer of Team Checkpoint seems doing similar motorwork to the original Yokomo as other motorbuilders but if you have a close look and compare with other modified motors you will find some additional modifications. At each side of the endbell there is a hole machined at the plastic base for improved cooling and inspection of the armature. And you will find again the slot-type brush and spring setup, typical for a lot of Checkpoint modified motors.
Any Checkpoint modified motors are hard to find and something of a holy grail for motor collectors, but early Checkpoint based on Igarashi or Yokomo teardowns are even more difficult to find than the Platinum versions.