Hello Detlef,
Congrats, a very nice piece, indeed! Let me know if you ever get bored with it...
I'd go with a generic Sunda attribution - I'm not convinced that it is possible to identify specific Cirebon features with swords that apparently had a pretty wide distribution probably including Sunda-influenced areas in southern Sumatra.
I'd guess that the "crown" was a flat or slightly embossed piece of silver. Not sure how it was attached traditionally - looks like it was merely glued in this case?
BTW, I'd love to see this blade etched!
Regards,
Kai