Hi Oganza! I just received this e-mail as a response for my request of information from Hamada & Sons on this shotgun:
Dear Mr.Ferreia.
Thank you for your E-Mail.
I think this shot gun were made by Matsui Gun Shop in Tokyo.
May be this is manufactured in 1950 & 1960.
Mr Matsui ceased his businness about late of 1980.
We are sorry our reply is so delay.
Shugo Hamada
Hamada & Son Ltd.
Do you know anything about this Japanese shotgun manufacturer? I did a web search and came up with this shotgun on sale at a shop in New Zealand:
http://www.guncity.co.nz/12g-matsui-side-by-side-xidp234507.htmlThere seem to be similarities to my shotgun but the image is not very clear unfortunately...