I have a glass negative with a pic of my dad in his navy whites... the envelope is stamped on the inside with Mori Photographic Studio, Front of Central Post Office, and Japanese characters. The front of the envelope is stamped with Japanese characters and 251. Can anyone help me out with this? Thanks!

You already have a keepsake of your dad in terms of a glass negative and an envelope describing the particulars of what it is. It would be helpful to know what specific information it is that you are wanting to know, please? Someone here just may be able to give you the answer to what you are wanting to know. If not, then perhaps someone here could point you in the correct direction in order to find out that which you want to know.

Thank you!