When Adam12 went into syndication in the Los Angeles area, the name was changed to 1Adam12. The same thing occurred with the offshoot Emergency!, which became Emergency!911. This may have been done to make sure people knew it was repeats and not the "first run" series that was still running on NBC at the time.

Did this occur in other markets across the US?

Also, why doesn't this occur today?

It was known during the seventies, and early eighties, that shows would often pick up syndication before their run was over, the perfect example of this would be shows like Emergency!, Adam-12, Magnum P.I., Miami Vice, and Star Trek: The Next Generation, all of which got picked up for syndication prior to their first run episodes finishing out, but, when certain syndication episodes were being aired opposite their first run counterparts, they would rename the syndicated episode, so as to ease confusion, or so they thought, sometimes it created more confusion than it was meant to stop, so, around 1980, the practice of renaming syndicated shows was abandoned. And yes, it did occur in other markets . . . example, I live in the Midwest, and I can remember syndicated epiosdes of Emergency! airing as Emergency! One, and synidcated episodes of Adam-12, airing as 1-Adam-12.