Hello, Wadehardin,
I'm not sure if you're asking for confirmation of a particular poster. If so, if you post the link, I'll take a look at the poster.
If you're asking a general question about the SW Style A 77/21-0, then I can confirm that this poster is original. It is, in fact, the first printing of the Style A and the one that was notoriously bootlegged with the subsequent "hairy belt". The 77/21, the 2nd printing, was not bootlegged.
I don't know where you got the information that the 77/21-0 was a reprint, unless by "reprint" you mean a bootleg "reproduction". Usually, when a poster is referred to as a reprint, it means an authorized commercial reprint and not an unauthorized reproduction (commonly referred to as a "bootleg".)
I hoped this has helped. And welcome to APF!
Jeannie