Duplicate Armor Identification Key

Date & Time: N/A
Frequency: N/A
World name: Midgardsormr
Character name: Kathein Lulin
Retainer name: N/A
NPC name: N/A
Monster name: N/A
Class/Level: WHM 70
Party or solo: N/A
In-game time: Constant
Area and coordinates: Constant
Housing: N/A

I have had a duplicate Armor Identification Key sitting in my retainer inventory for a couple months now, but I have grown too frustrated with it clogging up my inventory with no solution.

I have completed The Ultimate Weapon MSQ (The Praetorium). When I attempt to use the key, an error message indicates that I have already claimed the mount. I cannot discard it in either my retainer's inventory or my own.

I purchased a story skip shortly after the end of ARR MSQ to go straight to HS. I'm under the belief that SE threw me the key as part of the general ARR skip.

Any help would be appreciated. I detest this thing and just want it gone.