Need help dating this cocktail dress

I bought this dress in NYC in the 1980s. It has no labels at all. The only telling thing is a TABIT metal zipper up the back. The cutwork flowers appear to be hand-stitched as they are so delicately attached to one another to create a beautiful balanced pattern. I thought this might be a 1950s sheath/wiggle cocktail dress because of the nipped waist and the pencil skirt, but I am no expert. The material of the skirt seems to be a poly blend? Guessing the flowers are cotton/linen. The lining on the top is ivory and under the skirt it is black. The flowers are not fully attached to the bosom, or the back where they dip into a V. My questions:
1. What period is this dress from?
2. Any info about the cutwork floral lace that is both black and ivory. Is this unusual? What material are the flowers do you think? Is it hand-stitched?
3. Is this a wiggle sheath dress?
4. What is the time period of the Tabit metal zipper?
5. Any ideas as to the designer?
Any other info would help me greatly.

 

The lace does not appear to be cutwork, they look like pre-made lace appliques which were then sewn to the bodice. Or it could be Guipure lace which can be sold by yard and they are not individual appliques. It is not a sheath, as it has a waist seam, and it does not quite (to me) look narrow enough in the skirt to be called a wiggle dress.

But is is very pretty!

 

I agree with early 1960s, and the lace is not "cutwork" but as Barbara says.
I wonder if the dress was once part of a matching dress/jacket set.

 

Thank you all for weighing in on this with your expertise. I now see exactly why this cannot be called a sheath dress because of the waist seam. Would it be more appropriate to call this a pencil shift dress? It fits very close to the body. There is no slit in the skirt, and you must take small steps to walk in this. It is 12" at the waist, 16" mid skirt and then max 17.5" at end of skirt.

In regard to the lace, I also now see that it is not cutwork in the Irish or Italian tradition. I am attaching more detailed photos for you to see the stitching up close. It does not have any backing like machine made appliqué patches. The last pic is of the backside of the lace. It is plain on the underside. It is also not attached to the bodice, and the embroidery linking of the ivory and black is so unusual. I cannot find anything like this on the web at all, with the ivory and black mixed.

Could this be Guipure lace or Venetian wedding lace since there is no backing?

Have any of you seen this before? And is this lace machine made and linked by hand you think? Thanks for your help.

 

Looks like a chemical lace to me.

 

Why early 50s, as opposed to early 60s? Just wondering.

 

This also has the metal Tabit zipper up the back, black on dress side, and silver on the inside. On the back of the Tabit zipper, it says USA. This might help with the dating. Thank you.