
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1919
1920-1925
1926
circa 1920
1927
1927
1920
1924
1918
1927
1920-1925
1918
1925
1924
1955; 1830
1918
1918
1922-1923
1922-1923
1922-1923
1922-1923
1921
1920
2000-100 BCE
circa 1920
1923
1925
1922
1925-1927
1920
1924
1927
1926
1921
1926
1923
1924-1927
1934
1921-1926
1925
1920
1920
circa 1927
1920
1903 (original); 1982 (model)
1925
1772 (original); 1919 (model)
1990-96
circa 1920