
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1935
1935
1920-1925
1917
1934
1919
circa 1915
1936
1915-1925
1923 - 2015
1920 - 2007
1926
1931
circa 1920
1927
1927
1915
1920
1915
1924
1935
circa 1930
1928
1918
1914-1920
1914-1918
1936
1920-1929
1934
1935
1922
1932
1915-1925
1932-1936
1934-1935
1934
1916
1914
1931
1931
1915
1936
1927
1925
1930
1915
circa 1930
1920-1925
1917