Tested :
Dwarven Female key - Turned in by Dark Elf Female - Level 11 - Gave correct key which Zam shows as 17.
Result : This did nothing, no quest text or response at all and no faction hits at all. Also, not sure if this is important when I hailed the dwarf she said nothing about keys only the taskmaster.
Not sure if this is what you were refering to, but I did test it
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