I have numerous images of guns engraved by Japanese craftsmen but the one below is the only one that I can connect to Hamada. May I ask why you are inquiring? Do you have a model 12 that you think was engraved in Hamada's shop?
Yes I have one I believe to be done by Hamada and Sons in the late 50's. My friend has one that has a stock I believe to be done by daughter Emiko. I will send you some photos when I get back in town the week afetr next.