The numbers are supposed to be somewhat universal but there are exceptions. The letters usually indicate the shielding and types of shielding. For example one Z should mean shielded on only one side. Also, the correct bearing number should be etched into the bearing race rather than on the shielding. Bearings are only supposed to be 40% full of grease. I read years ago that the most common cause of bearing failure is over lubrication. Friction goes up when they are too full and heat is the main cause of failure. Second of course is contamination which is why most of them we use are shielded.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.