I don't think Coach was ever considered high end. In the 60's and on the Bonnie Cashin bags, they mostly used brass plating and the leather used was not as nice as on later bags. In the 70's and possibly early 80's, they used solid brass. A lot of those bags have very minimal hardware like tiny buckles, probably to keep the weight down, and the hardware isn't marked "solid brass". I had a bag from the mid 70's that had large brass buckles and they were extremely heavy. Dooney and Bourke used solid brass through the nineties - I don't know when they stopped. I was a little surprised when I learned this - in some ways, the D & Bs from the nineties were nicer than Coaches. In my collection, I don't believe that any of the Coaches with a serial number, which would be anything made from the late 70s on, has solid brass hardware.
I think Brasso might help but I think you are still going to see that texture of chipping.
I have one turnlock that is very loose. I figure it will break soon so I intend to replace it. I don't know if there is a way to repair it rather than replace it. The stores won't help you with turnlocks. I asked at both FP and factory stores and the SAs weren't even aware if JAX provided turnlocks. If I don't get the turnlocks, I'll probably try to send one of mine in for repair since it needs some stitching as well. I'd attempt the stitching on my own but if they aren't going to send me the turnlock, I might as well have them do both things.
There is a limit on how many hangtags you can ask for. If you've already gotten a few, they might feel you are abusing the system. They don't mind providing hangtags when they think you originally bought the bag from them, especially if you give them the impression that you are still spending money with them. A lot of resellers ask for a bunch of hangtags and they don't want to encourage that. If you ask for hangtags at a store, they don't keep track of how many you get so IMO that is a better way to go.
It can take about 6 weeks to get back a bag you sent in for repair.