Just recently at the MCACN show I had lunch with one of my Cleveland Chevelle car buddies and his friend. In talking with them I found out they both worked at the Chevrolet plant in Parma Ohio back in the mid to late 60's. My buddy is about 68 ish now.
They said they were both involved with drive shaft's and balancing, they made shafts for more than several Chevrolets'.
I specifically ask if they knew anything about the strips, they explained that when doing the code stripes, and while the shaft was still in the ballancing fixture, the guy might hold several paint brushes at a time while the shaft turned in the fixture.
So the one reason to post all this, they both indicated to me that one the the 3 strips was a shift code. If it was consistent, who knows ? And if not, that may explain why you'll see only two stipes at times.
Mike