Ford "wide five" Brake Drums

[mercman from oz]

Shown above are some front Brake Drums to suit the "wide five" Bolt Pattern. The top pair are marked 1936. If you look at the one with the red wheel mounted, you will see that the centre extension is much shorter that the ones marked 1936. I know that these "wide five" Wheels were only used between 1936 and 1939. What year is the one with the short extension and what years did they change from long to short? Thanks for your help.