Lace long dress - need help with dating the garment

[Mimimoo]

I have this long dress, but not sure what decade it could be from.

The top and bottom consists of blue velvet, and the rest is a black synthetic fabric with white lace over it. The zipper is white, oval and "opti" is written on it. No label.

I can take more pictures.


Thank you!

 

[Pinkcoke]

I would have said very late 1960s to early 70s.