Don't worry, you aren't the first to confuse these!
I agree with 80s. There were alot of these imported in the 80s. They weren't cheap, I remember them at good department stores, they were silk chiffon with glass beads and were often straight or drop waisted like the 20s. But the Made in India label, the back zip and the shoulder pads are the indicators of newer manufacture.
1920s beaded chiffon dresses will not have a zipper at all, if they have any closure it will be snaps at the side. If they have an import label, it will be Made in France. And of course, no shoulder pads.
Hollis