OFB-12

This is what they call: "hearing the bell, but not knowing where it is." But you don't forget to speculate...

The main goal was to initiate an exchange of information on this topic, what people remember/know (and not, for example, to prove that I know where the bell is). And now, thanks to two answers, a clearer picture emerges. Even if this picture is not news for some, it is no longer news for any potential tournament participant who reads it.