
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1910
1917
1919
1920-1925
circa 1915
1909-1910
1915-1925
1907
1926
1911
circa 1920
1927
1910
1927
1915
1920
1915
1924
1910
1910-1920
1908
1928
1918
circa 1910
1914-1920
1909
1910
1912-1922
1915-1925
1916
1914
1906
1915
1927
1912
1915
1910
1920-1925
1917
1910
1928
1918
1907-1917
1912
1907-1917
1925
1907-1917
1914
1924