 Standard steel wheels, pre 1968 trivia
I need an unbent, standard steel, 5-lug wheel for my 1966 convertible so I have been examining local possibilities. By 1968 the wheels were welded while the earlier ones had 12 rivets holding the rim to the center section which has the lug nut holes. 17 5-lug wheels of the same style were examined today with stamped codes on the center section ranging from 3MD (April 1963) to 6MG (July 1966). Obviously the 3D wheel is not from a Mustang while most of the others were likely Mustang wheels.
What does the stamped 'M' stand for that seems to be in all the Ford wheel date codes? Nothing? Mid-size? Other? Its not 'M'ustang since even the 3D wheel has an 'M'.
The date code is stamped on one of the raised spots near the wheel lug nuts. On 15 of the 17 wheels there was an extra 0.225" diameter hole positioned one wheel nut CCW (viewed from the curb side) from the date code. Two wheels from the same car (re-painted a metallic silver-blue on the curb side only) did not have the small hole. Those two wheels were both dated 5MB - February 1965.
Of what significance, if any, is this small, unused(?) hole? | 
