All 3 are valid numbers. They just are numbers for different things.
46M0861 is the FRU or FIELD REPLACEABLE UNIT. This identifies components that are functionally equivilent but may not have the exact same design. As products go through their lifecycles and get tweaked, they may have several revisions, circuitry changes, replacement ICs, etc. Two products that have the same FRU are suppose to be interchangeable even if they don't look identical.
46M0831 is a OPTION NUMBER or MARKETING NUMBER. It identifies the option when building a system that originally may have included other components, instructions, etc. While the option number may not change, what it refers to is subject to change over time. This may be on the card, but I don't remember them usually being present back when I dealt with IBM equipment on a daily basis. Usually it was the other two numbers.
68Y7366 is the PART NUMBER. This identifies this exact card and any card of the same exact design.
Or in other words, multiple part numbers may be under a single FRU, and multiple part numbers and/or FRUs under an option number.