Ian,
That's a real neat sword, congrats on finding a early untouched example.
I can't add much else that hasn't already been mentioned but I feel the sword can just as easily be far more to the Northern Laos when considering the age.
Here is an interesting link to bronze manufacture and history...specifically Rain Drums but totally relevant to the sword hilt...
http://www.lasieexotique.com/mag_fro...frogdrums.html
Gavin
PS, I forgot to add, re Ariel's note about the sword hilt orientation; Personally I see the current orientation as being correct in this instance for the specific sword type and age.