Empire Lauré 20 centimes blue (5x including 2 pairs) on cover 15-1-1871 transported by Boule de Moulins to Paris (arrival mark 18-2-1871 on reverse), fine/very fine with 2019 Christian Calves certificate. When Paris was besieged by the Germans in 1870-1871 the Boule (a hollow bullit) was a way to get mail to Paris. The Boule was filled with letters and thrown in the Seine, the purpose was the Boule floating downstream to Paris were it had to be recovered. Unluckily none of the Boules ever reached Paris. The contents of the recovered Boules were smuggled in to Paris by feet.