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July 13, 1922

White to play, can he castle?  No!  From retrograde analysis, we know that White's king has moved.

If it's White to play, what was Black's last move?  It cannot have been Ra1-a2 or Re8-f8 since either would have left the white king under attack.

Black's last move could only have been ...0-0, which means the rook at a2 was promoted from one of the pawns from e7, f7, or g7, any of which would have required either the white king or white rook to have moved.

(Solution by Mauro Castanho.)