TP-16 went though "mkI", mk II, mkIII, all with different effective mass.
Oringal TP-16 had effective mass listed as 16.5 grams, mk II and III was 7.5 effective mass.
"Which tonearm on yours?"
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
Hamlet Act 1