Help Id'ing Japan Letter Sheet Used By US Soldier In 1919

I recently acquired the pictured letter sheet sent by an American soldier serving in the American Expeditionary Force in Siberia in 1919. It's a fascinating bit of postal and military history.

Can anyone help with identifying this item, e.g., catalog number ("Sakura," I gather is the premier catalog for Japanese collectors), year(s) issued, denomination, what the inscription on the left says, etc.?

I can research easily enough the letter writer and recipient and how this item traveled from Siberia to its ultimate destination in Salt Lake City, but I need some expert help with the letter sheet's background.

Thanks!

Any chance of a close up, of just the stamp / indicia ?
I find myself squinting at the monitor.

Are we sure this is Japanese?

Yes, Japanese. The two left characters in the indicium were never used on Chinese postal items as far as I know. The indicium reads "military post/mail". Not listed in my old JSCA catalog; I'm wondering if it is a private design.

No expert here,
I cannot see any listing in Sakura

Sakura

Postal Stationery Page 322
International Mail Postal Cards Page 327
Commemorative Postal Cards
Seasons Greetings Postal Cards
Blue Bird Postal Cards
Heart Mail Postal Cards
Stamped Envelopes
Letter Sheets
Cards for Parcel Post

https://stampauctionnetwork.com/X/x122013.cfm

It could be 1949 rather than 1919.

Not really, the AEF as noted on the card, (American Expeditionary Force ~ Siberia) was stationed circa 1918-1922

(Japan were part of the allies)

The American Expeditionary Force, Siberia (AEF in Siberia) was a formation of the United States Army involved in the Russian Civil War in Vladivostok, Russia, after the October Revolution, from 1918 to 1920. The force was part of the larger Allied North Russia intervention. As a result of this expedition, early relations between the United States and the Soviet Union were poor.

U.S. President Woodrow Wilson's claimed objectives for sending troops to Siberia were as much diplomatic as they were military. One major reason was to rescue the 40,000 men of the Czechoslovak Legion, who were being held up by Bolshevik forces as they attempted to make their way along the Trans-Siberian Railroad to Vladivostok, and it was hoped, eventually to the Western Front. Another major reason was to protect the large quantities of military supplies and railroad rolling stock that the United States had sent to the Russian Far East in support of the Russian Empire's war efforts on the Eastern Front of World War I.

https://en.wikipedia.org/wiki/Ameri...rce,_Siberia

For the record, Japan issued 5 military stamps
(all 3 sen)
1910
1914
1915
1921
1924

Overprinted "gunzi" (Military affairs)

The idea, to give 2 stamps per month to each member of the army and Naval forces in Tyosen (Korea) and Manchuria or China, so that letters could be handled free of charge

Thanks for these observations. As rod222 notes, it is definitely 1919. That's when the US sent an AEF to Siberia to liberate a contingent of Czech fighters and to protect American-made military equipment that was sent to Eastern Russia.

I'll reach out to the International Society for Japanese Philately to see if they can provide more color.

For the record, attached are close-ups of the "stamp" and the inscription.