
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1920-1925
1917
1919
circa 1915
1915-1925
1923 - 2015
1920 - 2007
1926
1931
circa 1920
1927
1927
1915
1920
1915
1924
circa 1930
1928
1918
1914-1920
1920-1929
1932
1915-1925
1916
1914
1931
1931
1915
1927
1930
1915
circa 1930
1920-1925
1917
1928
1918
1932
1925
1914
1924
1955; 1830
1915-1917
1918
1914
1914-1918
1918
1915-1918
1925-1928
1916-1917