I would applause your collaborative speculation abilities!
You are right both erilaz
, this is an envelope/package for a set of postcard and description note to celebrate 25th anniversary of Taisho emperor's marriage, issued on 10 May 1925. I guess dandow
has a beautiful embossed postcard with a few stamps on, to show us after this envelope? I follow up reading of some other images;
image 2; -read each character from right to left, from top raw;
tai kon (imperial marriage) ni ju
go nen (25 years) ki nenn (anniversary)
e ha gaki (post card)
Toppan Insatsu Kabusikigaisha (Toppan Print Inc. still exits https://www.toppan.com/en/?_ga=2.24....1654772814)
"HB" patent print-plate production
A pair of 2, price 20 sen
Teishinsho (first 3 letters - Ministry of Communications) Hakko (issuing) - read from right to left, same as the large title of image 2.
Modern characters are written from left to right, also many of them in these images are simplified - even for me not easy to read.