Cmdr. Armand Balilo, PCG spokesperson, said that two of the aircraft will be brand-new while the remaining two will be "Excess Defense Articles".
He added that PCG inspection team will leave for the US by next week to check on the aircraft.
Balilo also said the Americans expressed interest in transferring the four "Sherpa" to the PCG.
The C-23s will augment the existing Norman Britten Islander planes being operated by the PCG for maritime patrol missions.
The "Sherpa" is a small military transport aircraft built by Short Brothers.
The C-23A and C-23B variants are variants of the Short 330 and the C-23B+ is a variant of the Short 360.
It can carry 30 crews and passengers and has a top speed of 281 miles per hour.
The last C-23 "Sherpa" in the Oklahoma Army National Guard inventory is parked outside of its hanger for the last time before being turned into the Army Aviation Command.