That's interesting, what did the letter say?
As far as I know the film was called blue harvest during production and then revenge of the Jedi up to the last minute so it could be something produced after the film was released.
This is the email I received in 2012 from the owner of the design company:
Your vest is an authentic
Star Wars: Return of the JediCrew Give-Away,
I was an owner of & the designer for L P DESIGNS from 1978-1994,
we worked directly with local movie studios, the music industry, and the like,
we did only 'real' work, i.e. never 'bootleg' merchandise,
because of our careful censorship we worked with the top companies in the USA & abroad ........
I will be happy to mail you a letter stating your vests authenticity,
let me know where to post the letter,