This is one of the early Type 30 bayonets produced. This was manufactured by the Tokyo arsenal prior to the great earthquake in 1922. After "The Great Earthquake", all production was moved to the Kokura arsenal, but the 'stacked cannonballs' arsenal stamp was retained an used by Kokura.
This particular bayonet is from the 6th series as indicated by the relatively low serial number (669900).
Features include a hooked crossguard, a bright, fullered blade, contoured bird's head pommel,
screws and washers to secure the contoured grips.
Note the extra blade inspection mark under the arsenal mark on the ricasso.