The engraving is similar to that done in Japan for GIs in the 50s and 60s - possibly Hamada & Son
This was my first thought as well. Many an unusual firearm was purchased through the PX by GIs stationed in Japan and then taken to a Japanese engraver for "enhancement". However of the ones I've seen over the years this engraving just doesn't look right. Additionaly; The wood has been upgraded here as well. I don't ever remember seeing a Japanese engraved gun from that period with this feature.
Of course as a first step the factory should be contacted to see what,if anything,is in their records.
Jim
