There's a serial number lookup at this URL, if you ever need it: http://www.berettasupport.com/applic...search_new.htm
I live in a fairly arid environment, I'm wondering if that accounts for the finish difference/rust. I can forget how forgiving this climate is to firearms.
I carry my px4 compact daily. It's fired everything I put through without fail (except steel cased tulammo) and has been very accurate. It's a little chunky for an edc, but hey, so am I.
I have a compact PX4 9mm that has 1864 rounds through it without cleaning from every kind of ammo (Tulla, Wolfe, WWB, & lots of reloads mostly lead) without any issue. I carry it every day as my CCW and trust the h#ll out of it. I have a full size that has 9016 round through it with any issue except a bad batch of reloads i put out that didn't have enough crimp.
Bottom Line is the PX4 is an outstanding weapon.
I've noticed a propensity to FTF if the user doesn't have good solid grip, have to be very sure not to limp wrist. I've not personally had an issue, but two teen girls and a twenty something guy I've let shoot it at a barbecue that hadn't shot before all jammed. I took it back and did a quick mag dump and didn't have a problem. Also second the comment from someone else that it doesn't love steel cased ammo like Tul. I love mine, and I trust it, but I think you can make a good argument that something like a G19 or M&P9c would be a better choice for most people. Simpler action, better availability of parts and holsters and mags, etc.