The metal zip had been invented in 1891 by W Litcomb Judson of Chicago USA. He patented a clasp locker system of fastening constructed from a series of hooks and eyes with a clasp lock for closing and by 1893 the metal zipper was in sizeable production.

But many 1920s and 1930′s dresses were finished with press studs or buttons because of the unreliability of the zipper mechanism and so most garments were still designed with button fastenings until the 1950s when improvements in zip manufacture were acknowledged. Zippers were usually put in the side seams of dresses, skirts and trousers until the early 50s. Later they were used in the centre back of dresses, skirts and the centre front of trousers.

In vintage terms many enthusiasts believe that a metal zipper in a garment is a good rule of thumb that along with other factors indicates a garment is probably pre 1960. Plastic zippers were available in the 1930s but were not widely used until the 1960s when the YKK Corporation stepped up manufacture in the US. 

Vintage zipper brands to look out for are the Lightning (maufactured by ICI) in the UK in the 1940s and 50s and the Talon zipper from the USA, again in the 1950s. A word of caution though; the presence of a metal zipper does not guarantee the age and authenticity of a vintage garment. Unscrupulous dealers have been known to insert old recycled metal zippers in to 1960s and 1970s pieces to make them appear to be 50s or earlier.