Helvetia is the nation of which Sieze and the girls is a part of, the name being the old Latin name for Switzerland.
Is in an armistice with the Roman Empire, and have been so for 6 month by the time the series starts.
Used to have a draft that have been abolished by the time the series started.
Have had Archdukes as head of the state for a long time, unknown if it still have.
Shown to be around North East Asia, more specifically Japan, according to a map in the Episode 13 OVA.
Goverment System? Presence of archduke: Suggests Monarchy (note, alot of nation still have monarchy as a symbolic head of state)
Nationalization: Could suggest a lot of things, communism not being likely
No music: Could suggest fascist control, or cultural depreciation of music
Low recruitment age/ girls in military: Suggests either desperation for recruits, relative legal equality of sex, or very militaristic state.