Grice on the inverted "A" (substitutional)

From an online source:

"According to M. J. Cresswell and Irving H.
Anellis, [the inverted A] originated in Gerhard
Gentzen, "Untersuchungen ueber das logische Schliessen," Math. Z., 39, (1935), p, 178."

"In footnote 4 on that page, Gentzen explains
how he came to use the sign."

"It is the "All-Zeichen," an analogy with [rotated E] for the existential quantifier which Gentzen says he borrowed from Russell."

But never returned!