A - Prehistoric Era, until ~1200BC  Infinite   Dugouts, rafts
B - Legendary Era, ~1200BC-500BC    700 Years  Early galleys, sails
C - Hellenic Era, ~500BC-200BC      300        Biremes, Triremes
D - Roman Era, ~200BC-400AD         200        Large galleys
E - Byzantine Era, ~400AD-800       400        Crewed weapons
F - Dark Ages, ~800-1200            400        Center rudder
G - Medieval Era, ~1200-1400        200        Complex sail rigs
H - Age of Exploration, ~1400-1550  150        Galleons
I - Elizabethan Era, ~1550-1750     200        Early SOLs
J - Napoleonic Era, ~1750-1850      100        Frigates and SOLs
K - Transitional Era, ~1850-1880     30        Early steamships
L - Early Armor Era, ~1880-1910      30        Early BBs
M - World War 1 Era, ~1910-1930      20        Submarines
N - World War 2 Era, ~1930-1950      20        Aviation
O - Cold War Era, ~1950-1980         30        Missiles
P - Space Age, ~1980 on              40+       Space weapons