Magi Surami question

[IJBall]

OK, I've got a question about Magi Surami in Port K.:

I accidentally got into a tussle with him, and when I killed him he dropped a 'Bluish Key' (which I guess must be different than the 'Bluish Key' that Father Tyrus gives you in Eastwillow).

Anyway, I tried Surami's 'Bluish Key' on the lock on the door to the mysterious Port K. Mage's house, but to my surprise, it didn't open it.

So does anyone know what Magi Surami's 'Bluish Key' opens?!
TIA.

[Randomizer]

There were a few other places where you used to be able to get duplicate keys, but that's the last one that hasn't been fixed.