
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1935
1910
1935
1920-1925
1917
1934
1919
circa 1915
1909-1910
1936
1907
1915-1925
1926
1931
1911
circa 1920
1927
1910
1927
1938
1915
1920
1915
1924
1910
1938
1938
1910-1920
1938
1935
1938
1908
circa 1930
1928
1918
circa 1910
1914-1920
1914-1918
1936
1920-1929
1934
1909
1910
1935
1922
1938
1938
1932
1912-1922