I wouldn't be surprised if the signature on the door was photographed and then recreated as faithfully as possible, most likely with a decal. I'm basing my decision on this photograph of the car as shown after filming, compared to a picture in the current auction catalog. Obviously the livery is totally different (reasons in the article) but also, I can see enough differences in some of the letters that lead me to think that the signature was preserved as well as possible throughout many changes of ownership, but there eventually came a time that it was no longer practical for various reasons to try and keep it intact and as is.
The 't' and the 'e' in 'Steve' are the most obvious examples. Every letter 'ueen' in 'Mcqueen' show variances. I believe the note was photographed and then a new vector file was created in Adobe Illustrator with some artistic license employed to fix problem areas. Some of the discrepancies I'm seeing might be parallax and graining because of the two different views and the age of the photos, but in my mind, there's enough evidence to point to this being a very faithful reproduction of the original. Maybe the original door exists with the signature intact, and this is a replacement door.
http://www.yahoo.com/entertainment/car-week-steve-mcqueen-porsche-130000183.html
