A New-To-Me Miroku 1763/66 Charleville

[Rum River]

Found one on Gunbroker and now I own it.
I would like to find out a date of manufacture, but so far haven't had luck tracking down some kind of serial number lookup.

This one has the 'NAVY ARMSCO. RIDGEFIELD N.J. U.S.A.' legend on top of the barrel by the lock.
On the left side opposite of the lock is 'MADE IN JAPAN' and the serial number 1xxx.

I've tried doing some searches but haven't yet found what I want.

Can anyone out there point me in the right direction?

 

[Rum River]

After making some calls the closest I've come to a manufacturing date is "probably in the 70's, maybe in the 80's".

Still checking............