If I understand correctly, the "zero(s)" at the start of the serial number actually are simply circles, indicating that the rifle was re-barrelled (twice seems to have been the usual limit, but three have been reported).
The term "training rifle" has been much misunderstood in regard to Japanese Type 38 rifles. The military turned old but serviceable rifles over to the equivalent of our college ROTC for training firing live ammo. Those rifles were not deactivated and were/are perfectly safe to fire with standard ammo. They were also turned over to police and para-military organizations for various purposes.
Other rifles were made for training of the equivalent of our High School ROTC; these were made of cast steel or cast iron and are non-standard; few parts will come anywhere near fitting a standard Type 38. Quality varies; some used worn out barrels, but most are smooth bored, with the barrels made from steel tubing. Some appear to be steering shafts of automobiles, screwed into a larger piece that had the chamber. In some models, the chamber part is one piece with the receiver. Those were made only for use with lightly loaded blanks, (standard 6.5x50 ball will not fit) and I am sure the boys had a lot of fun with them until they "graduated" to more serious weapons.
Jim