After the Rebbe’s traditional blessing on Erev Yom Kippur of 5729 (1969), the Rebbe’s secretary, Reb Leibel Groner, wrote to the Rebbe that “some pointed out and are worried that in the Bracha of Erev Yom Kippur after Mincha, in which the Rebbe Shlita blessed Klal Yisrael, the usual blessing of “a Chasima and Gmar Chasima Tova” were not mentioned as in every year.”
The Rebbe answered:
הרי נאמרה בפי’ [=בפירוש] – וכענין בפ”ע [=בפני עצמו] – לאחרי סיום ברכת הת’ שי’ בסיום עריוהכ”פ [=ערב יום הכיפורים] ובהתחלת יום הקדוש.
It was said clearly — as an independent statement– after the conclusion of the Bracha to the Bochurim שי’ at the conclusion of Erev Yom HaKippurim and at the onset of the Holy Day [of Yom Kippur]
This answer was incorporated as a footnote to the edited transcript of the Bracha, published in Likkutei Sichos vol. 9 p. 382. ■