This cache is to honor all those Peace Corps School Construction volunteers who have passed through Libreville on their ways to numerous villages in the nine provinces of Gabon. The first volunteers were here in 1963 and were here until the program closed in 2001. The initial schools built in the 60's had wooden windows, but with the groups arriving in the late 70's and after it was recognized that windows made of brick would be as effective in keeping the classrooms secure and would hold up a lot longer. The cache is located where some of those same style of window bricks, which hint at the cloister walls of religous communities hence the name claustra, have been used in the construction of a wall around a house.
After you find the cache you might knock on the door and see if someone is home who can give you more info on Peace Corps Gabon and Gabon in general. It is posted by palmier but maintained locally.
Congratulations to KralikX for being the FTF