Japan Envelop With Or Without Postal Connection?

I acquired this envelop in a large lot of turn of last century Japan covers and I have been wondering if it has any postal connection. Unfortunately for me, the main text is in seal script, which I am not able to read.
I think the seal script starts with Dai (big) then ?, 2, 10, 5, year (perhaps 1925?). Don't know the rest. However, the year in the western calendar is strange to see in seal script, which usually has the year in regnal years.
Any help with this would be appreciated.

Since there has been no response yet, I will throw out a semi-educated guess on this envelope.

I seem to vaguely remember from that octagonal logo that these were sleeves for parts of sets of post cards. Do you have anything in the group that would be that? And is it the right size/width?

The long boxed imprint is "second page, first group, price: gold 20 sen".

They never wrote year dates like that back in the day. In the octagon, it's "Daima (? - a guess), 25th year, ????" Third line is art "something". I want to say "ehagaki" (picture post card) but the middle character is a traditional/one unknown to my references.

Yes, the word in the bottom line is "ehagaki". I found a cursive form of the "ha" (leaf) character in Oreste Vaccari's Standard Kanji that has essentially the same shape as the one on the envelope.

The characters in the second line that you couldn't decipher are "kinen" (commemoration). I'm a fan of a J-pop group called Melon Kinen-bi, which means Melon Commemoration Day.

I'm fairly certain that the second character (from the right) in the first line is "kon" (marriage). If so, then that first word is "taikon", which Nelson's kanji dictionary translates as "imperial wedding". The whole inscription would thus mean "Imperial Wedding 25th Anniversary Commemorative Picture Postcard(s)". Since the Emperor Taishô and Empress Teimei were married in 1900, that would match up with the pencilled date of 1925 on the envelope.

I would applause your collaborative speculation abilities!
You are right both erilaz and hy-brasil, 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)

image 3;
Toppan Insatsu Kabusikigaisha (Toppan Print Inc. still exits https://www.toppan.com/en/?_ga=2.24....1654772814) "HB" patent print-plate production

image 4;
A pair of 2, price 20 sen

image 5;
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.