Help with identifying dates/material: White Wedding? Dress/Under Dress?

[whitewolf]

Found in my mother's vintage clothing collection. No label. Size is probably 2-4. Metal zipper is stamped "MATIC". The fabric is a little shiny, stiff & transparent. Any thoughts? Thank you!

 

[Rue_de_la_Paix]

It is likely organdy (usually cotton) or organza (silk). It does have the appearance of an under dress.

 

[poppysvintageclothing]

It also looks like it could be muslin. I agree that it does look more like an underdress, I can't help but wonder what would have gone over it with that extra long zipper at the back.

 

[anothertimevintageapparel]

It could also be a toile version of a gown.
I have had some before, along with the finished gown or dress.