I just talked with Khun Bancha yesterday...
For the questions, regarding to Dahbs ID, You will need to generalrize typical characteristics for Dahbs from different age and locale. So you will need to examine "population" of Dahbs.
Sometime, you will also need to associate "art" on the sword with other native stuff (pottery, temple etc.)
For Dahbs ID, Khun Bancha seems to use tang tyle/geometry, tang tilt, spine curve, edge curve, point style, tapering style, ratio between different regions, blade material etc.
In many case, he also ID from hilt and scabbard. Only problems s' that some blades are come with new hilt or scabbard (or both).
The story 's even more complicate. When some Dahbs were made to order and shipped to another city for sale. Smiths had produced the Dahbs in end-user style with a hint of the smiths characteristic. Another problem 's smiths themself migrated from one city to another (as prisoner of war).
To overcome these problems, you will need to study them for decads (which I think you were
) and travel to many places in SEA (seems to be a some problem for you).
I, myself, lack of decades experience. So I will need to learn from Khun Bancha and his [Dahb expert] friends. I invited him to this lovely forum and I hope that you may pick up some idea from his collection
For Khun Bancha, is it better to show only one Dahb at a time with an extensive description about how did you get an idea for its age and locale.