Thanks for your input Jim. I'm aware of Silver Frost, Silver Blue, etc. Medium Silver Metallic was offered later in the '66 model year, but it is not listed as an exterior color on any paint sheets I've seen. From the book "Mustang 1964 1/2-1968" By Tom Corcoran (and other sources) Medium Silver Metallic is a special order color & had a blank warranty plate paint code.
This car is a May 1966 special ordered Mustang (six digit DSO) with a blank paint code which is supposed to be Medium Silver Metallic. If anyone can point me to the correct paint mix code I'd appreciate it.
Those same pages or rewrites of the same info is in the Library
You statement appears to be in conflict. On one hand you write that you believe that Medium Silver Metallic was offered late int he year but you also write it was a special order. Your reported 6 digit DSO seems to support the special order part of the statement not the first part
Special order colors have been discussed here a number of times. If the salesman could he would steer the customer towards a color being used on a different car line, if not the color was chosen from 0the color chips in the Fleet color book. All those colors were identified by a code not a name and the number corresponded to the back side of that chip and used on the formed that was filled out for the special paint. Very late in the year "new" colors for the up coming year were slipped into production or made available also through the process
Any color other than the RPOs would have been a special order so the color you mention was not in itself a "special order color". If you believe it was a color from another line (only reason it would have a name associated with it then you need to find what line it is. Lacking that you need to find a sample of that color and compare it to the chips from a 66 Fleet color chip book to find a match. Even then the color codes and numbers will not be very useful 50 years later from past experience. I've owned a number of special order paint cars