Actually, I think it's TROUBLED WATERS. It's not that I remembered the exact name, but I know that the special key in that story HAS a longish name, so I'm pretty sure that's it.
In Troubled Waters, the killer used a Curtis Clipper to make a master copy of the Ving keys that were used on board.
I don't recall ever seeing that - perhaps its in a later episode. I did the new tab thing and typed in Rosenvinge key and what is a r k. I did not see any site which associated Rosevennge with a key.