THE FIVE PERIODS OF IMPERIALS EAGLES ISSUES
PERIOD I → 8 May – 7 July 1864
Initial distribution of stamps to district post offices.
PERIOD II → 8 July – 19 Sept. 1864
Introduction of consignment numbers and wider distribution.
PERIOD III → 20 Sept. – 31 Dec. 1864
Stabilisation of postal operations and cancellations.
PERIOD IV → 1 Jan. – 31 Dec. 1865
Expansion of the network of district offices and sub-offices.
PERIOD V → 1 Jan. – 31 July 1866
Final period of use before the collapse of the Empire.