Well acrylic points to later rather than earlier.
I'm going to venture that this is late 70s, but it definitely
has an earlier feel to it. The scoop neckline and sleeves
are 70s, however my initial thought was that it was
an earlier dress, revamped along the way. The fabric
rules that out however.
Thanks for posting this.....I love mystery dress posts, they
are fun and informative for all of us.
Sue