This is a quite normal French letter from 1809. 17 Bourges is the place it sent from. France was divided into numbered districts and 17 is the number of the district. ( You can see a list of these numbers at(
https://fr.wikipedia.org/wiki/Liste...7ais_de_1790 ).There is an about 2 inches high figure written over the address and that is is normally an indication of the amount due and this is probably a "2" indicating the amount due in decimes. 1 decime was equal to 10 centimes, so I there was a due of 20 centimes on this cover. Covers like this one are quite common so I think there is no risk that it is faked.