Real Vintage Old Hollywood Gown

I wish I knew how to date this dress but I can’t say which era it’s from. Tagless and purchased at a NYC boutique. The zipper is metal so I believe it’s before the 60s. Front zipper down center. Some pleat action at shoulders. The material feels like silk or thick satin. Tie belt. There are stains as shown which I never tried to remove so can def use a dry clean. Lying flat 14” across chest 51” top to bottom