Archie,
The Castle key that you show (without the "Service is King" wording) has the word ENTER in smaller lettering. The other one I show below has larger lettering.
The small lettering one that I have is gold colored on the back.
The larger lettering one is white on the back.

If the larger letter ENTER is one that you don't have, I would be happy to trade for one with the "Service is King" wording since I don't have one of those.

If the larger letters is indeed an unknown key and you need a better scan just let me know.

Best Regards,
Murph