on the case keys, you are correct that was his question, my bad.... i was wrong for not reading the op's post compleatly as i now see the header plainly states "chassis" i will leave the reply as is, with the note about Case locks as changing/editing the whole reply might cause more issues
on the case lock, i have a xw6200 case that now holds a asus x99 board and i have 2 xw8600 case's and the xw6200 uses a diffrent key from the 8600 you are correct in that HP only used a very limited set of keyings for the locks so it's fairly easy to get a key that also matches other systems it's also possible to drill out the existing lock and replace it as a replacement lock/key can be bought on ebay
i keep a small container filled with keys from unknown (in most cases) systems/servers/removable drive enclosures, that i sometimes use when a key gets lost and in a few cases had the correct key!