The numbers are the model numbers and denote differences in chassis.
The 300 ones are OEM so could be anything, usualy missing adjustments on the damper or the u-turn function. I dont think theres any way to tell from the number what it is so you'd have to look at them and/or ask.
The 400 ones all have the same damper, but different steerers and crown. Cheepr ones (lower number) have steel steerers and a solid crown, the more expensive have a hollow forged crown and an aluminium steerer.
The spring is independant from the number so you can get a coil sprung pike with the lightweight steerer and crown.
As far as i know they dont make a non u-turn coil spring model.