Don't worry about it -
Any insulation which was going to fall out probably fell out over 60 years ago. You'll do more harm 'fixing' it than leaving it alone.
Rockwool insulation was used back then - an excellent choice, by the way, and not at all like the dangerous asbestos we all worry about today.
If it's absolutely troubling you, a high-temperature silicone (used to seal chimney joints) would work, as would a stainless steel bolt and nut - but, yikes! Not worth it.
Do ask questions, please - we all learn from these things and enjoy them. We are so not one of those forums which scream at people that 'that question was answer in 1937, please reference the archives and don't ask again'. I've left some radio repair clubs because of that nonsense - ask away!
Any insulation which was going to fall out probably fell out over 60 years ago. You'll do more harm 'fixing' it than leaving it alone.
Rockwool insulation was used back then - an excellent choice, by the way, and not at all like the dangerous asbestos we all worry about today.
If it's absolutely troubling you, a high-temperature silicone (used to seal chimney joints) would work, as would a stainless steel bolt and nut - but, yikes! Not worth it.
Do ask questions, please - we all learn from these things and enjoy them. We are so not one of those forums which scream at people that 'that question was answer in 1937, please reference the archives and don't ask again'. I've left some radio repair clubs because of that nonsense - ask away!