I have read the advice many times in various places that one should not use the old needles that come with the purchase of a machine or the ones that come in old needle tins or the ones found inside a newly purchased machine. By and large based on my albeit still limited experience, I would say this is very good general advice. The needles found inside a machine will always be a mix of dropped used ones and spills/drops of new ones. The needles in old tins seem to be similar-people seem to have dropped used needles back into the tin with new needles. Also old needles, including NOS ones, often have corrosion on their tips that may or may not be visible to the naked eye.
Nonetheless, despite this good advice, I find it an interesting pass time to do an archaeological exploration of caches of old needles. Things get added to my personal museum/collection of different types of needles--and there are so many different types. And many needles are salvageable.
As I have mentioned elsewhere here, I use a jeweller's loupe to cull needles, even/especially new needles, many of which (depending upon their source) have badly malformed tips--I will sometimes skip this culling for needles from highly trusted, known-good sources.
I do the same with old needles. It is very easy to differentiate between a used needle and an unused one using the loupe.
I also use a cork from a wine bottle (Henkel Trocken pictured below but not necessarily or especially endorsed

) to polish needles which have seemingly corroded tips. I push the needle fairly deeply into the cork and rotate them back and forth 15 to 20 times vigorously. Needles, to greater or lesser degree individually, are magnetic being ferrous metal, their tips are magnetic poles, and so flakes of plating and corrosion are attracted to them. Such flakes remain trapped in the cork, and if there is actual corrosion, anything loose enough that it might fall off, it is also removed by the cork, the loose flakes anyway. The needles can then be reassessed with the jeweller's loupe. Many that would have been deemed culls on first inspection are found to be quite serviceable after the cork polish.
I also use the cork on all new steel needles before playing a record. Even with the absolute best of steel needles, I still find small fragments of metal caught on the poles/tips of the needles. These are always removed by the cork.
The needle stuck in the cork below is a lone example of a type I have never seen before. The shaft becomes slightly more bulbous as it approaches the tip. I haven't tried it out yet. If will definitely go into my collection.