The easiest way to figure out which version you have, generally, is by checking for the TV station ID logo which is usually shown during the cartoon. Here is a link showing the various known versions with their logos:

http://www.starwarsholidayspecial.com/versions.htm

The only one I know of so far that was broadcast in the US with no logo during the show was the WCBS one in New York. But if it has the newscaster breaks intact with the "fighting the frizzies" bit, the logo is shown there.

Hope that helps,

--SKot