This is a common occurrence in Japaneseicon firearms where there is not a clean cut designation in serial numbers between a change in components.
If your forestock wood and rear band shows no evidence of ever having a mono-pod installed, I would not be looking for one to put on it. TJK 37th mono-pods are proof stamped on the right side of the band spring with the "sha" stamp, and the foot of the pod itself is the standard rounded foot, not the flat foot of the Kokura 20th-21st series rifles. Look in the dust cover grooves for any bluing wear. If it was issued with a cover, you will see wear. Most, if not all original long cleaning rods I have observed are not proofed, but show a slight plum color in the bluing. I agree with Singer and J-Rod to leave the rifle "as is". If you are purchasing from the GI's family, it's a good chance that this rifle is "as manufactured".