Nice post, thank you and thank you J.AW.
On yours xpensive the drawing shows 'gun interrupter gear'.
The 601 fired its cannon through the engine V and strait through the airscrew hub AFAIK.
The shells did not have to miss the prop blades so why did the gun need interrupting?
Edit: Sorry I just answered my own question.
The interrupter was for the other two cannon firing through the prop arc.