If I recall correctly none of the V15 styli regardless of series were interchangeable. I have an original V15 , III and IV.
One distinctive difference between each generation of the V15 is the shape and dimensions of the Pole Pieces and Stylus Brass Housing. This means that the styli are not interchangeable from one generation to the next. They do not provide a proper fit, or alignment, between the Magnet and Pole Pieces.
The above is a quote from Timetable/history of the V15 cartridge.
One distinctive difference between each generation of the V15 is the shape and dimensions of the Pole Pieces and Stylus Brass Housing. This means that the styli are not interchangeable from one generation to the next. They do not provide a proper fit, or alignment, between the Magnet and Pole Pieces.
The above is a quote from Timetable/history of the V15 cartridge.