http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Level 7 has c1968 imprint date and no edition statement.
Grade levels K-6 are designated with colors: Beginning level, yellow; Level one, blue; Level two, red; Level three, green; Level four, orange; Level five, purple; Level six, brown; Level seven, Life : its forms and changes; Level eight, Matter : its forms and changes; Level nine, Energy : its forms and changes.