It has a few elements of earlier in the 1940s, and even 1930s elements (back ruffle, gathered bust,) but that back zipper is throwing it off. However it is hard to be sure as it is very wrinkled and hung up on a hanger, and we cannot see the actual silhouette of the skirt and way it falls from the waist area. I cannot see where the waist seam is (if there is one), or how wide the skirt is. These 2 clues alone are very helpful to us in dating it.
If you can iron it and show it on a person or mannequin that would be very helpful.
I think perhaps it was made in the late 40s by someone who still liked the earlier styles. Possibly it may have been altered from an earlier dress, with the zipper added at a later date.
Can you tell if the skirt is bias cut? If so, then it is likely altered from an earlier time (1930s), as a zipper would not appear on a bias cut dress. Ditto if it has a high waist seam which is another 30s element.
The bustle back started in the very late 1930s out of Paris, and then was revived again after the war ended. Is it just a row of ruffle there, or is it a true bustle back? Again, we cannot tell with the way you show it.
I agree it looks a lot like rayon satin.
