A stunning status sword Thomas. I love the Peurawot like throat section.
These open sheath types are quite common amongst a variety of knives and swords from the region, I'm sure some simple google image searches will turn up many.
Attached is another sword type from Sumatra, albeit a later sheath, it is of the type found with these weapons, both ceremonial, status and combat.
The knives are not typically open backed, but do carry the elaborate hooked motifs at the throat.
Here are some variants from within the Forum pages.
http://www.vikingsword.com/vb/showthread.php?p=33079
http://www.vikingsword.com/vb/showpo...1&postcount=15
http://www.vikingsword.com/vb/showthread.php?t=18416