reubent, I agree with astro58go: Good question. And astro offers a nice introduction to the topic. One could go on and on and on about how to determine the answer for particular LPs and record labels. But, here’s the thing...
First pressings are not the right guide to finding the best sounding records. So, what are you looking for? If it is "collectability" then yes, seeking out first pressings may make a record more collectable and therefore more valuable. Similar to first editions of books.
But if your objective is finding the BEST SOUNDING pressing, first pressings are not always the best. Generally speaking, earlier MIGHT be better. If it is from the first master, first mother, first stamper off the mother, first few records off that particular stamper... But there are so many variables:
- When during the pressing run with that particular stamper was this record pressed? There is NO WAY to tell this and stampers wear out.
- What quality vinyl was used during the pressing run? Good or poor? Noisy?
- Was this even a really good mastering job that created the lacquer or was better mastering done in a latter generation? Who was the cutting engineer?
- Was the temperature of the vinyl going into the press optimal? Did it cool optimally before being removed from the stamper?
I will buy multiple copies of the same record for $1 each from the used bins and then compare them by listening. I often find that new "high quality" remasterings made in recent years outperform many of my early pressings of the same records, PROVIDED the master tape is in good condition (always a challenge as tape ages).
Of all the indicators I know to watch for in looking for good pressings, they are the mastering and cutting engineers and what in what pressing plant the record was made. So, I DO examine the deadwax when buying used records. For some of the codes in the deadwax, see:
https://richmondaudiosociety.com/2012/07/02/dead_wax_inscriptions/ Overall, I’ve long ago given up on obsessing over first pressings for the sake of finding a first pressing.