Ok, I hope I'm not hogging this thread...
It is possible to guess where a keris is from by looking at natural materials such as wood, and to some extent the metal. However, this is an inexact science, and we mustn't forget that trade has being ongoing between the islands for centuries, so materials can be exported/imported. The best bet is to look at the style of workmanship, the form and the motifs. There are no easy guidelines that can teach one how to make a judgement call on where an item is made. Instead, one has to look at as many examples as possible, and 'internalize' the style. Once that is internalized, it is a lot easier to see that a particular specimen is "not quite right". I'm sorry I can't answer your question the way you want, but there is really no shortcut.
To help you along, here's a link to Dave Henkel's Tajong/Coteng page.
http://www.kerisarchipelago.150m.com...ge/Tajong2.htm
As for motifs, I attach pics of 3 south Sumatran hilts for your reference. You may see why I thought your hilt has Sumatran influences. Though the same motif may exist in Java and even N Malaya, they are not executed in quite the same way.
Michael's coteng is from southern Thailand. The region is politically Thai, ethnographically Malay. The tension between these 2 factors are clearly evident in the reports of daily violence in Southern Thailand.