Are there any cracks going to the out side? In that same area on my 60 there is a chunk broke out on one side. A guy I know that has used 60's all his life told me that will happen if water gets in there and that it would be ok. I'm sure it has been like that since the 60's because it didn't set outside after my grandpa bought it and yes it has worked just fine so far. Others may have a different opinion on it though. Just my 2 cents.
Geoffrey