Ah, I remember those days - I had the same situation at home.

As the article mentions, you could dial the 67 prefix to block your outgoing caller ID on an individual call.

With the blocking-of-blocking, you had the opposite - the 82 prefix _disabled_ outgoing caller ID block on an individual call, allowing you to call subscribers that blocked blocked numbers.

I think my folks finally decided to drop the caller ID blocking after the phone company switched from 7-digit to mandatory 10-digit dialing for all calls. It was just too many digits to dial with the prefix, especially since half the time you would dial without the prefix, get the "blocked" message, then dial again with the prefix.