“The letter… is dated for the civil New Year.”
-The letter is not dated.

“sent by Rabbi Nissan Mindel on behalf of the Rebbe”
-This is misconstrued; all Russian letters in those years were handwritten by Rabbi Mindel as mazkirus did not have a Russian typewriter. Saying that it was “sent by the mazkir on behalf of the Rebbe” is akin to saying that any typewritten letter was “sent by Rabbi Mindel/Rodshtein/Simpson on behalf of the Rebbe.”

“The signature “M. Zeide,” written in the Rebbe’s own handwriting, as was customary in such correspondence”
-In fact, the signature “M. Zeida” was also handwritten by Rabbi Mindel, “as was customary in such correspondence.”

“годоми” should be “годом и”
“М. Зейде” should be “М. Зейда”

The rebbe dictated it to Reb Nissan Mindel; and it was sent to Reb Mendel Futerfass (in Tchernowitz, USSR) prior to Rush Hashonoh (first of Tishrei).