In short

ID Card Looty Bay Bank is a ID card for the building “Looty Bay Bank” in Downtown. It opens: vault. Behind the door: Gold Bar. The key fits only this place.

KeyBuildingDistrictOpens
ID Card Looty Bay BankLooty Bay BankDowntownVault

Where it is

The building is on the interactive map. All keys, doors and safes of the city: Locked doors, Safes and containers, the key guide.

The game data does not list where this key drops or is sold, so we do not guess.