50s Caramel Dress

Very interesting long sleeve dress. Background is a caramel, orangish light brown with darker brown florals. Wide neck. Zipper down back with hook and eye at waist and top. Stiff fabric. Reminds me of curtains! Darting at bust and elbows for flattering fit. No tag. I believe it to be 50s or 60s. Perfect for a dinner party! One small stain (see pic) slightly lighter on back at seams (gaping?). Otherwise good vintage condition. Laying flat, 18" pit to pit and 14.5" at smallest part of waist.