I just came across this. Anybody know if this information is still
current (does the condo continue to exist?):

The Peru Border with Bolivia

This border was defined by the Polo-Bustamante treaty of 1909 and a
Protocol signed in 1925; a condominium over Lake Titicaca was also
established. At the time of the 1929 treaty between Peru and Chile,
Tacna was returned to Peru on the understanding that its boundaries
would be the same as those laid down in the treaty which Bolivia had
signed with Chile in 1904. Bolivia subsequently questioned the
legitimacy of Tacna's boundaries and came to view that part of the
border as a de facto arrangement, which, for that matter, has since
remained unchanged. Both countries refer to the area between
Mauripalca and Jalaropampa as "Section IV of the Southern Border".

Thanks

LN