As a former system builder, I happen to have about a dozen sets lying around (and an A4000), so...
The key sets all have a number marked on them, ranging from "101" to "1102". NOT ONE single key fits the A4000 I have.
Either the diameter isn't right, the wall is too thick to allow it to engage, or the "pin" on the barrel (looks like the front sight on a rifle) doesn't allow it to turn the lock.
So, yes, they are keyed differently.
And the reason I had so many of them? We NEVER used 'em - it was too simple to just open up the computer case and disconnect the "KEYLOCK" connector, and the cases we used had easily defeated lock mechanisms. We called them "Delayed-Theft Devices", instead of "Anti-".
banzai