I have a some belt conveyor drive motors, SEW make 18.5 kW. The bearings installed as per data sheet & name plate are "6312-2Z-C3-K52". Another 15 kW motor has 6312-2RS-C3-K24.
I wonder what this "K52 & K24" stands for? Checked with SKF, FAG, NTN, could not get it.