That middle rib you called, is the "caping" or point, as explained in Spirit of Wood. And you also can see how identical this "caping" as to the coteng's.
It also appears in some aged keris tajong sheath.
The build shape is identical to the cirebonese sample that Sajen had shown, no doubt about it. However the "caping", "shoulder" and the "third eye of Shiva" is all the characteristic of a pattani's origin.
Cross pollination is obviously the reason why it is so identical to both region's design. Let's not forget the empus from pattani also originated from Java / south sumatra.
Of course I might be wrong too. Let's learn from each other