Blue knob "Marconi" Style
Knob/Skirt diameter: 2,55cm 
Hole diameter: 0,55cm (easily drillable for 1/4? shafts) 
Height with skirt: 1,8cm 
Height without skirt: 1,6cm 
This knob has a similar look like the Neve Marconi knob but it´s not an original Neve knob.
You can drill the shaft to your needs or upgrade it with 
set screw kit to use it as replacement knob for your gear.