Question: List all state classes when successors were formally installed on June 22, 1868.
Schema: create table table_2417340_3 (state__class_ varchar, date_of_successors_formal_installation varchar, PRIMARY KEY (state__class_))
SQL: select state__class_ from table_2417340_3 where date_of_successors_formal_installation = "june 22, 1868"