Japanese Type 30 Bayonet - Manufacture date?

Hi All!

I thought I might reach out to the collective wisdom of the group in order to answer a question regarding a Type 30 bayonet I recently picked up.

As you can see from the attached images, the variation of bayonet that I have is pre/early war as it was manufactured with a bright blade, fuller, contoured birds head pommel, and has the hooked quillon. The manufacturer's mark is either Tokyo or Kokura arsenal and carries a proof stamp in the ricasso below the "4 cannonballs" mark. Serial number 941920 does not have a series marking before it on the pommel. There are two inspection marks on the pommel.

My question for the group is if, based on the information provided above and on the pictures, it is possible to determine the month and year of manufacture? I am asking as the Tokyo arsenal used the 4 cannonball mark from 1897 until 1936, at which point Kokura took over the use of the mark. It would be nice to have a definitive manufacturer of the bayonet as well as when it was made. It is in great shape and retains the factory sharpening 2/3 the length of the blade.

Any information or direction you can point me to learn more about this piece of history would be appreciated. Thanks!