help dating this beautiful blue rose print dress

[Ineke Veenstra]

And another one

I bought this dress a couple of months ago and I really hate the fact that it is just too small for me! I would love to wear it because it is so cute..

Although i don't fit it, I would like to know a few things about the dress:

- How old is this dress?
- Are the blue strains original?
- Why is the zipper way too long? maybe replaced?
- What kind of fabric is used for the lining?
- Why is there a tag that says 11 k? why on that spot, and what does it mean?

This dress:
- has a beautiful blue rose print on a cotton fabric
- top and skirt are lined with a very soft fabric
- zips at the back with a metal zipper from 'zenith'
- has a mysterious tag that says '11 k' on the inside between shoulder and zipper

 

[Pinkcoke]

I would put this as early 60's.
I can't really say if the hanger straps are original without seeing where they are attached to the dress, but it's likely they are period and I wouldn't removed them unless they were uncomfortable when worn.
If the zip extends past the opening of the dress fabric is a replacement with whatever they had, it probably came from a housedress/dressing gown or similar.
The lining looks like cheesecloth cotton to me. It wrinkles up if you let it dry naturally, it's best to iron it a bit while damp to keep it full length and smooth.
I can only guess the numbered tag is a manufacturers label, perhaps for the machinist etc.