That's all true except that 'sealed move' wasn't invented at Fischer-Spassky time. Actually, it was used all time since official tournaments started, i.e. since 19th century. Currently, it became obsolete because games are not interrupted more, i.e. players are required now to finish game during one playing day. Snail mail play is also extinct. The reason is quite simple: computer age.

>Dragan,
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>That's called a "sealed move". It's used primarily in tournaments when play must be suspended due to the end of the playing day, a power outage, time restraint or other non-playing situation; it's also used when players are playing a game by snail mail over long distances without the aid of computers.
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>This technique was brought to light during the Bobby Fischer - Boris Spassky matches back in the 1970's. Because there were no player clocks used, each move took far longer than a normal game.
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>HTH.
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>>>SCHOOL in the US – 1957 vs. 2008
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>>In chess, there's an expression which I can't translate... "to put a move in envelope". That's what I'm doing now. I wrote down my prediction. I may be back to see whether the move was right.