Hello Alan,
Ok, let's assume for this mental exercise that this blade really was from the land of Jawa...
We're only looking at the major classifications and being Jawa-centristic pretty much ignore any peripheral origins...
I already stated that the blade clearly is from the Mataram line.
While the garap and some of the prabot may be a tad stiff (lambe gajah, gandik, etc.) and the greneng not cut to perfection, it might still be old Mataram; I'm just trying to imagine 2 centuries of maintenance by acid washing and just about all of these detractions will be pretty much gone for good or restored to current tastes!
The elephant trunk seems to have quite a bit of substance and will tend to loose less material from erosion; however, by modern standards it could be a bit heavier to begin with. This, coupled with a slight slant of the gandik, would make me to also consider Madura Sepuh. If this was an old survivor from any European kunstkammer, I'd need a lot more time for detailed comparisons. Given a more realistic timeframe of about 200 years, I'd be inclined to opt for the old Madura classification.
So, to wrap things up: Do we have a Madurese craftsman living in Palembang and trying to copy old Mataram style?
Regards,
Kai