I don't think it's primer. The destructive effects of our friend the sun.. It's a little exacerbated by the direct sunlight but I guess we just got used to it. Another pic below.
Pretty remarkable what a little paint can accomplish. Hopefully paint technology has advanced a lot since the last coat....That last stuff aged terribly
It has been almost 50 years (assuming this is the first time since it was built). I'd say that's a pretty good period of time for the paint considering the abuse it has taken.
Thanks for the link Alvin. Forty-something years is indeed a pretty impressive run for a coat of paint. I retract my previous statement. To be honest I was making the (baseless) assumption that this wasn't the first re-paint job.