Beyond "Original Pressing" LP designations

In the never-ending quest for superior sonics, it is often found that the "original pressing" of a certain LP is the best (not always, but often it IS the case). Further, it is generally accepted that, even among original pressings, some sound better than others, those nearer the beginning of the pressing run being superior, as opposed to the end of a run when the master is wearing thin.

I have around 2,500 LP's collected over the years and have gotten back into vinyl, in earnest, over the past two years. Now, in addition to broadening my palette of music, I'd like to upgrade certain favorites, with respect to condition.

Can the vinyl experts among us detail how one can identify the specifc "vintage" of an orignal pressing? Do the stampings on the inner groove area render clues? I would guess that such is highly label-specific, but would be interested in any information you'd be willing to offer with respect to any label.