18thC Ottoman Flintlock Holster pistol restoration project.

[Atlantia]

Acquired this once rather fine large holster pistol and thought you'd all like to see it in 'as found' condition.
Besides, I'm still scratching my head about where to start with the cleaning and restoration.
Looks Ottoman but who knows what marks might be under the rust (some elements could be European?).

Any comments, help, suggestions of where to begin greatfully received.

Best
Gene