Hard to know. I have a model 06512, or KSSM-4F-S-I, or the stainless single six 32 hrm, with the short "plow handle" grip with the Ruger Ivories attached.
Looking at the right side of the gripframe, cast into the frame there is only a "302" on the bottom, with a "T" in a circle on the right side and a sideways "K" on the left side. A worker scribed the last 3 digits of the serial number up near the ears of the grip frame.
Looking at the left side, there are no cast markings, but an "I" is scribed down near the bottom.
No other markings that might identify how Ruger used a designation for the short grips.