Thank you for contacting Mearto with your appraisal inquiry.

It is a beautiful Gunne Sax dress. Such vintage clothes are being offered at auction on a regular basis.
I would date the dress to be from the 1970s. Based on your description and the photos it appears to be in good condition without any restorations or faults. It has a lovely design that is typical of Gunne Sax. The floral material adds to the overall look of a very special dress.
Second hand clothes and accessories are usually sold by the brand names and Chanel and Louis Vuitton are the most expensive brands. However I am quite sure that this lovely dress would attract both buyers and collectors if it came up for sale even though it is not one of the most expensive brands.
The estimate provided is for a well-advertised specialised online designer clothes auction, where I believe the dress has the best chance of realising its fullest potential. However, there is no measurement for the sentimental value you might attach to the Gunne Sax dress. Retail "asking prices" can be higher and vary.

Please let me know if you have any additional questions. I’m happy to help.
Thank you