Flying suit

Any zipper specialists out there? I have a flying suit that I’m trying to date, and am thinking that its zippers might be helpful for this. They were made by The Lightning Fastener Company, from Britain, and, as you can see, the pulls have patent dates of 1919, 1920 and 1925, all very early dates for a zipper. Would it be safe to assume the suit dates to the late 1920’s / early 1930’s?

 

According to this, the company was founded in 1925 and they started suppling fasteners to the aircraft industry, including "aviation suits", in 1939.

https://www.gracesguide.co.uk/Lightning_Fasteners

Debora