
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1920-1925
1917
1919
circa 1915
1915-1925
1923 - 2015
1920 - 2007
1926
circa 1920
1927
1927
1915
1920
1915
1924
circa 1930
1928
1918
1920-1929
1915-1925
1916
1915
1927
1930
1915
circa 1930
1920-1925
1917
1928
1918
1925
1924
1955; 1830
1915-1917
1918
1918
1915-1918
1925-1928
1916-1917
1928
1924
1927
1915
1926
1922-1923
1922-1923
1921
1922-1923
1922-1923