Complex sentence: The 1769 seal was a double sided seal with the King's arms on one side and the shield from the colonial on the other; it was stolen in 1775 by American forces and never returned.
Split into simpler sentences: The 1769 seal a double sided seal with the King's arms on one side and the shield from the colonial on the other. The first seal was stolen in 1775 by American forces and never returned.