M-40-17017 was a Ford spark plug wrench that was included with the tool kit on V-8s from 1933-1938. These work GREAT on Ts for those who wish to save the paint on their cylinder heads. The beveled end fits beautifully in the spark plug well on the Model T engine and allows the plug to be loosened or tightened WITHOUT chewing up the paint along the edges of the well (not the case with a standard T spark plug wrench). I carry them on all my Ts. Box end is 11/16. I have script and non-script - your choice. $10 plus shipping per wrench.
Lot of takers on these - guess people are tired of tearing up their engine paint. Pile is shrinking - rapidly.