The above photograph shows a standard C foot joint for a silver Muramatsu Flute
For many years the C Foot Joint has been considered as "standard" with B foot joints (Bb Footjoints - rare) being considered as extras or as a special option.
In the UK the C foot joint is the most common option with many players who need a B Foot Joint fitting it only when needed. In the States, I suspect the B Foot Joint may be becoming or has become the most common option - at least on higher quality flutes. Feedback required on this comment
The above photograph and notes are as accurate as my knowledge of the subject permits
If anything above is factually incorrect, or if anyone can usefully improve or add to the above notes then please feel free to email me at john@fluteweb.net