I am very interested in this thread as I posted two photos of my underbody as the fourth post. I too have tried to figure out the underbody primer color without luck. I have had at least four others look at the car on a lift and we all fail to see any red primer, black/gray primer. or slop paint. Turnall's car was bucked on October 28, while mine was October 21. It's hard to believe that Ford could have had the underbody primer spray jets off for an entire week. Does anyone have a Metuchen car that was build around this time to help us understand what is going on? Some other possibilities: maybe Ford experimented with a primer that failed in the field soon after it was applied? maybe Ford did experiment with some cars without primer to see what would happen in the field? Nothing I can think of makes sense except that a variety of cars did not get primer, but why? My car was shipped to the first owner in Ohio and stayed there for a period of time, then to Missouri, Nevada, California and Arizona. The second owner bought the car in Arizona in about 2002 with 22,000 miles on it. I bought the car in Arizona in 2012 with 24,000 miles. The Ohio and Missouri winters would have been devastating on an underbody without primer.