Dating knit dressdress

[Jenny]

I found this from a 95 years old lady. I am not exactly sure how old is it.

 

[Circa Vintage Clothing]

Are there any labels, Jenny? I think it's likely to be '70s but if you can tell us more - eg, what sort of zipper it has (nylon, metal?) and the fabric composition (wool, cotton, acrylic, a mix?) it will help. Thank you.

 

[Jenny]

The zipper is metal. I am not sure about the fabric. :(