Thank you. I'm more of a newbie here, Ellie has been doing this for like a decade now... Even longer, perhaps?
Older bags have numbers only on cards they come with (but most sellers don't keep those). Newer bags have large fabric tags inside the zipper pocket with some info & a serial number, but those are more like model numbers. They're not unique to each bag and don't really tell what month/year the bag was made, like some other brands' serial numbers do. The three-digit number on the other side of the leather tag doesn't really mean anything, and not all bags have it.
Authenticating PS bags is mostly just getting acquainted with how they should look so that when something's off, you can see it. Most of the fakes we see here in this thread are easy to tell since they're really poorly made. But there are some that are quite, quite 'good'. So it's important to see all the logos, front side, back side, lining, etc. to be sure. It helps that this brand is not as popular as it once was.
^^ Thanks so much for sharing! Excited for my purchase to come now, thank you for helping me with it! Do you know if PS are pretty good with giving a new dust bag? I know some brands are happy to give you one if you ask, but others not so much.