The Bronze Dorje is the sixty-fourth treasure that can be found in Uncharted 2: Among Thieves.
The Bronze Dorje is found in Chapter 18 - Heart of Ice. You know the gear that you ride twice? Not the first one! The gear near the very bottom, just above the water level. You ride its outer surface up once, jump over to the left, and then ride its outer edge up once more. This is to allow you access to an area you'll need to traverse to proceed with the chapter. However, if you ride the outer edge of this gear up to the very top, you'll be able to jump to a horizontal wooden beam. Once you've pulled yourself up, you can begin to jump rightward. Jump to the right, and keep moving forward, jumping from beam to beam. You'll eventually come to an isolated, completely out-of-the-way platform where this treasure is hiding. It may be one of the hardest treasures to come across in the entire game.