Yes there were Separable zippers by Hookless before the 1930's for sure. I have seen some dated earlier as well. I have seen zip sliders dated pre 1920. It was still new tech though,even in the 1930's.Hi Jay
I think I wrote before, maybe in this thread, that Hookless didn't make a separable zip.
Well I was wrong.
This past week I found this blog which has a NOS Hookless zip;
Schott NYC claims to have been the first company to put a zipper on a jacket in 1925. The pictures used to illustrate this claim generally...vintageleatherjackets.blogspot.com
They must have been rare.