Congrats on an exceptional razor in amazing condition! I bet you're counting the hours for it to arrive
When it does, be sure to post some hi-resolution pictures.
I own one of the last Iwasaki Tamahagane Western Razors that Shigeyoshi Iwasaki ever produced (number 1901.6), procured by Harrelson Stanely from Masayoshi Hiraide in Sanjo city. If my house was on fire, it's the only object I'd take with me.
I recently saw pictures of a Iwasaki Tamahagane Western Razor marked 1406.5 that had a picture of a very similar box. I don't know whether the box was original to the razor however. The box was black instead of green and bore the tamahagane stamp. Otherwise they are very similar. The box might be helpful for dating purposes. I have posted 2 pics below. Do you have any idea when yours was made?