Domestic Postal Rates during the Usage Period Mail Type 1 Jan 1900 1 Oct 1916 1 Sep 1918 Letter < 20g 10H15H20H Letter < 250g 20H Letter per additional 20g 5H Post Cards 5H10H Post Cards with preprinted indicia 8H Printed Matter < 50g 3H5H Throughout the period, 1H was equivalent to 1 French Centime