I just happened to measure a standard one yesterday.
Active coils = 23
Active Length = 200mm (this doesn't include the collapsed coils at one end)
Coil OD = 20.7mm
Coil outer dia = 3.24mm
Coil inner dia = 14.22
Mean dia = 17.46mm
In my TX, 84mm stroke, 11 ft-lb in 0.177, gives 37% efficiency. Very good springs.