Wow, didn't know it was broken as it look whole in first photo.
It had two sound holes and a single slot with round ends plus a cast mount.
No marks (common is a size near the mouth).
Crude casting with voids.
Best guess is late 1800's maybe very early 1900's.
These are a brass like alloy so ultra sonic clearing should be ok to get the dirt off.
Even broken it is still a good find.