Treasure Chest Thursday: A Registered Envelope from Washington, D.C.

This envelope is 9 1/2" x 4 1/8".  It feels like some kind of kraft paper, similar in weight and texture to a paper shopping bag.  The paper is brown, and the printing on it is primarily red, with some black.  The front of the envelope has handwriting in blue and black; the back has three postmarks.

The return address on the envelope is the U.S. Marine Corps Headquarters in Washington, D.C.  It is addressed to Jean La Forêt at:
J L LA FORET QM SGT RET
R.F.D. #28 -ASHBY ROAD-
OVERLAND MO.

The dates on two of the postmarks are November 30, 1920 from the Navy Department Station in Washington, D.C.  The third postmark is dated December 2, 1920, when the envelope was received in St. Louis, Missouri.

And . . . there's nothing in the envelope.  We should be getting used to this, right?  So again we don't know what Jean received, but he kept the empty envelope.  It couldn't have been for a stamp collection, becaues this envelope doesn't have a stamp on it.

The large handwriting doesn't seem to match the business orientation of the envelope.  The envelope came from the Marine Corps and was addressed to Jean with his retired rank, yet the writing says:

Souvenirs
Some[?] for Album
Société de Geographie – Alger (translation:  "Geography Society, Algiers")

None of that seems to be related to service in the Marines, does it?  Jean's reference to Algiers made me think of his position as Vice Consul, not his re-enlistment.  Maybe the envelope contents were something Jean left in Algeria when he rejoined the Marines, and the consulate forwarded them to the Marines to send to Jean.

Jean also noted in the lower left corner the day he received the envelope:  December 3, 1920.  And now that I've noticed that, I've realized that this envelope came chronologically before last week's list of Jean's physical ailments, because that page had the Vallejo, California address.  Jean and Emma went to Missouri when they returned from Algeria and after that came back to California.  Well, that's a good example of the need to analyze all the clues before coming to a conclusion, isn't it?

There are also three numbers stamped on the envelope:  110 in the upper right corner, 84204 near the lower right, and 157334 near the lower left.  Nothing on the envelope gives any clue as to the purpose of those numbers.  Maybe someone reading this knows and will be able to explain them?