Smyslov Seals

Continuing with the Geller - Smyslov game from the 1956 Candidates Tournament at Amsterdam, the diagrammed is about 25 moves after the position shown in Smyslov's Grandmaster Moves. Black is ahead an exchange, but White's Bishop pair and the unsafe position of the Black King have kept White in the game.

The game was adjourned at this point and Black sealed.

Candidates Tournament
Amsterdam 1956
Smyslov, Vasily

Geller, Efim
(After 41.Qh2-g3)
[FEN "5r1k/p5p1/1p5r/2p5/2q2n2/P1P1BBQ1/5PP1/2R3K1 b - - 0 41"]

What was Smyslov's sealed move?