That portion of the suffix normally refers to the lubricant used in a sealed bearing. The K24 is Dupont Krytox 240AC. As an example see https://www.abf.store/s/en/bea...Z-C3-K24-ZEN/1045454.
Unfortunately I don't know what lubricant the K52 is referring to. Are you certain of the number?
Also helpful to us here would be the manufacturer of the bearing, if you have it.