The Silver Offering Pot is the seventy-seventh treasure that can be found in Uncharted 2: Among Thieves.
The Silver Offering Pot is found in Chapter 22 - The Monastery. Elena will dash off automatically following the cutscene, so you should chase after her. It's in that direction that you'll find not only the way forward, after Schäfer, but another treasure as well. After jumping over the severed bridge, you'll have to pull yourself upward in order to continue. But before doing that, drop down off of the platform you're on so that you're hanging off of the right side of it. Adjacent to you should be a red-colored wooden beam that you can move over while hanging, granting you access to a little alcove containing this treasure.