Mukden serial numbers for the type 38 are:

1-38,000
5,000,000-5,065,000
and 65,000-79,000 which are sometimes misidentified due to characters resembling a "3" in front of the serial number

All were made between 1934 and 1940, 117,000 were made. All Mukden rifles have the same buttplate through the entire production run.

Mukden also produced the type 38 carbine serial numbers

1-2000
600,000-628,000
and series 6 28-000-43,000

For a total of 45,000

All data is from Japaneseicon Rifles of World War II by Duncan O. McCollum