Point taken Detlef. Sounds like you have experience in Betel Nuts!
The knife pictured by Chris is the kind of example mentioned in the book by Silva and Wikramsinghe, but no mention of really early ones. I do believe it is of traditional South Indian/Sri Lankan design, it is just finding the reference that may be difficult! I do have a nice early one somewhere with an inscription (just don't ask me to find it!), but not earlier than 17th Century
