Hi Norman,
These interesting hybrids are I believe Bengali, and I have been told thier primary purpose was for the sacrifice of doves, however I cannot recall the source of that information. I have seen these catalogued with similar description, but it seems the eye of Kali is typically seen near the blade tip, much as in the ram dao. This weapon appears probably mid 19th century.
Having said that, I will also await Spiral's observations
All best regards,
Jim