Ian,
I wouldn't find it odd it for a member of the Philippine resistance to have the primary symbol of the resistance on his sheath. BTW the sun symbol is found on a number of South American flags and is also part of Masonic iconography. On a u-tube video, the presenter says that many members of the Philippine resistance were masons (Kirby Araullo, The Forgotten Meaning Behind the Sun on the Philippine Flag,
https://www.youtube.com/watch?v=xFG9w2KCSXI).
I am aware that Lee's photo is a backside view of the sheathed knife. That's why I said "reverse". That notwithstanding, if the sheath is worn on the right, the diagonally transverse suspension means that the tip of the sheath will project out in front of the wearer and the throat will open towards the back of the wearer. In addition to that, the buckle will be behind the sheath towards the back of the wearer. The only way to properly wear this sheath is on the left. If you have any doubt of this, I will be happy to post pictures of me wearing one of my examples. Once on the left and once on the right.
Sincerely,
RobT