I generally find that the bell on the Olivetti Lettera 32 and its' relatives is pretty disappointing. No matter what you do to adjust it, you never get a really loud and strident ring. However, I did have a 1964 L32 on my bench yesterday, and improved the bell vastly by unscrewing the fixing screw and putting a small washer between the bell and the frame.. Sadly, you cannot do this with later versions. The bell is rivetted to the frame at the factory !