>>>>>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.
>>>>
>>>>Not completely extinct. I've been playing via mail with a couple of opponents since I was in high school.
>>>>
>>>>FWIW I'm also an avid CW (morse code) ham operator.
>>>>
>>>>Some things just don't die.
>>>>
>>>Do you mean you still play via mail?
>>
>>Yep. Just a tradition.
>
>Snail mail or email?
>
>Chess by mail is such a very different game than face to face that I would not have expected it to die out. I would, hoever, expect the technology to change.

By US Mail.