Picture number M30210 (picture courtesy of Shannon Zeigler) Markings on the top of the receiver ring. The top character is the number 3, the second character from the top is the number 10, the third character from the top means year, and the bottom character means model. Hence, 30th year model.
Picture number M30220 (picture courtesy of Shannon Zeigler) Markings on the left side of the receiver. The symbol at the right of the serial number is the arsenal logo and indicates that this rifle was made in the small arms factory of the Tokyo Arsenal.