It is interesting that you say “400/360 No2”
I’ve only heard of it being called 360 No.2
Of course, it IS based on a 400 case, the 450-400 3” which has no relation to the other 400/360s. Why it was called the No.2 I’ve no idea except that it was a new 360 based on a larger case much the way the 500 No.2 was based off of the 577 case.
On the other hand, the 400-350 No.2 was simply a different loading of the very same 400-350 Rigby case.
It does get messy, the way these cartridges were named!