New to Fenix 5x - Advice for buying second hand

1. Charging port- turn it over and inspect the charging port. All for contacts should look the same, 4 equally silver (aluminum?) color. If 1-2 are dark, discolored, or look worn out then don't get it. Some were good and some were bad. You can search this forum for "corrosion" for photos. 2. Plug in the charging cable to USB and it should start charging with minimal fuss, or at least acknowledge the fussiness required to get it charging up. 3. The buttons should all work. 4. On the band, on the buckle side there should be 2 "keepers" but if not these are cheap to get on Amazon/ebay but it's good to know.   (This is based on my experience with F5, not sure how extensive the corrosion problem was in the F5 family).