Agree with the above. Differences between one pressing run and another can be dramatic. For the most part, each pressing run requires a new stamper, which introduces a variable. Further, different production engineers or plants often made their stampers from different master tapes.
Collectors spend hundreds of dollars for the most desirable pressings of their favorite LP's. Even two LP's from the same pressing run will vary, the earlier tending to fuller dynamics and greater low level detail. As the stamper wears down from each use, so do the sonics.
Unless you have electron microscopes for eyes, there's no way to tell any of this just from appearance. The information scribed in the dead wax may provide clues, depending on the record label.
An additional perspective: were these two LP's ever cleaned? If so how?
If one took two identical LP's and cleaned one really well while leaving the other uncleaned, the clean one would sound notably louder and clearer. This is true whether an LP is 30 years old or 30 minutes, though the 30 year old one will often be harder to clean effectively.
