Vauxhall Motors used the 12 name for two different cars in the 1930s.
Vauxhall Light Six1933 Vauxhall Light Six ASY type The 1933 Light Six was available in two engine sizes, 12hp and 14hp. It was updated for the 1936 Motor Show with a rounded grille.
Vauxhall 12-41939 Vauxhall 12-4 I Type A total redesign introduced in September 1938 and given the 12-4 name, the new model featured a longer six-light body based on the Vauxhall 10 and a 4-cylinder 1.4-litre engine
This article does not cite any sources. (June 2019)
