The part number is simply a unique numeric identifier for the device. There is really no way to use the part number to decipher what you have. But it is an easy way for data handling systems to keep track of unique devices.
The catalog number is an alpha-numeric value what has specific meanings attached to the various locations in the number. For example, without looking at anything and having no specific knowledge of that part I can tell you that the card is a 3-axis motion card, simply because all the the 1756 motion cards reserve the two locations occupied by the "03" to indicate the number of axes the module is capable of controlling. I can also tell you, as Mark already did and in the same way, the card is based on series A hardware because of the "/A" on the end. We wouldn't be able to tell you any of this based on the part number unless we just happened to know exactly what that part number was.
Phoenix Contact does the same thing with model numbers and part numbers. But they publish both in their catalogs. Rockwell only publishes catalog numbers.
The moral of the story is if the catalog number matches and you have the right firmware loaded into it the card should be good to go.
Keith