Study closely and you will see this block has a lot of surface rust scars on the pad area. I suspect a mild pass under the decking stone to clean it up was done so likely the whole head area was exposed and rusting. My 396 conv was taken apart by the previous owner after a rod bearing locked the motor in the 70's. He had since passed away and the car and parts sat in his back yard exposed to the weather. I bought the car and had to have the block decked to clean the rust off the exposed head mating surfaces (including stampings) so most of the VIN and prefix left behind is very-very light but still readable and there are still rust scars. Back in the 80's preserving a number wasn't thought of, with me at least, so when I had seen these pictures, it sure reminds me of what I went through.
I'm still curious where these photos came from.