There is a connection
between the station at Rue Jean Jaurés and the pneumatic postal
network in Paris, but there is none on the supposedly complete 1909
map of the system. The map on the stamp is not dated so it might be
intended to reflect the system as it might have appeared between 1870
and 1909 with a link that was closed or destroyed before the 1909 map.
Until there is more definitive information we cannot say with
certainty that there is an error.