Zippers in vintage clothing?

If there is a thread about zippers already please let me know...

If not, here is my question...

I know enough about vintage clothing to know most zippers started to appear in clothing in the late thirties/early forties, but what is the earliest zippers were used in vintage clothing? I have some 1920's/early/mid 1930's pieces that use the old style metal zippers, these pieces come from the movie studios, and a lot of the pieces I have seen from the studios really seem to be quite different from the normal clothing of the era. Anyone have any insights?

Some threads on Zippers and their history.

http://www.thefedoralounge.com/showthread.php?t=6076&highlight=zippers

http://www.thefedoralounge.com/showthread.php?t=28200&highlight=zippers

http://www.thefedoralounge.com/showthread.php?t=19518&highlight=zippers

and one specific to the Powder Room

http://www.thefedoralounge.com/showthread.php?t=16512&highlight=zippers

Just a reminder: most topics are already out there somewhere and using search can turn up tons of info. In this case, I merely typed zipper in the search window and scanned for Zipper in the thread title, to get whole threads about them.