My experience in these things brings me to the sand blasting suggestion for more than just one reason. One of these reasons is that often these things have been painted a number of times, often with very poor paint. So this is what you may have under all that. The other thing that I have seen is that because it has been painted a few times (possibly) detail has been lost under all that paint. When you sand blast it and paint it, it often will "pop" much more, often blown away "pop" that was buried before.