This style hubcap was used on Whippet 96 from introduction in June 1926 till Jan 13, 1927 - (before serial no 49431) when the script was changed to read "Whippet" instead of "Overland".
A similar cap was used on the 1925 - 1926 six cylinder Overland 93 but it had a thread to suit 2 3/4" x 16 TPI hub.
