Collect all silver rewards from the indicated level to unlock the corresponding object model.

Bolivia Redux: All silver rewards in Bolivia (level 8).
Bolivia: All silver rewards in Bolivia.
Croft Manor: All silver rewards in Croft Manor.
England: All silver rewards in England.
Ghana: All silver rewards in Ghana.
Japan: All silver rewards in Japan.
Kazakhstan: All silver rewards in Kazakhstan.
Nepal: All silver rewards in Nepal.
Peru: All silver rewards in Peru.