It is definitely heavier than a 20 centimes cover, hence the need for an 80 centimes rate. It was mailed from Angoulême (PC 83) in the Charente department to Rochefort — Rochefort-sur-Mer in the Charente-Maritime — Charente-Inférieure department.
Here is a detail of the stamp.
The stamp has a line brake.
Here is the back:
Here is a detail showing the Rochefort-sur-Mer postmark.
Here is the map from Angouleme (lower right) to Rochefort (upper left).
Here is the letter (it's a commercial invoice/bill):
https://www.transkribus.org/
Jou
Roy
COMPTOIR D'ESCOMPTE
Angouieme, le
D'ANGOULÈME,
1861
CHARENTE.
Créé par Décret impérial du 7 septembre 1854.
Messieurs Roy Bry N C á Rochefort
629 - 25
Je vy confirme mes lettres des 1. 3. 4. 5. 6 et c avec F
lad
Cavec F
J'ai reçu la vôtre du 3 Al
109
à votre crédit sous réserve.
Indus Neffets montant a F. 8739-16 Suit Bordin a bas, dont crédit et avis de réception a l’ae-
J’ai l’honneur de vous saluer
Dr Don
P. P. - Spéciale
Le Directeur,
Myn
Borderean.
CHANGES
Tours
INTÉRÈTS
No
Sommes.
Valeur.
Lieux de Payement.
Echéances.
Taux. Produits.
à 6 0/0
Courir
R Chateauneuf
frans
Vur
bognaro
Surgerés
Jarnue
Cognure
Jarnac
Google translate:
ou
Roy
DISCOUNT BANK
Angoulême,
OF ANGOULÊME,
1861
CHARENTE.
Established by Imperial Decree of September 7, 1854.
Messrs. Roy Bry & Co. in Rochefort
629 - 25
I hereby confirm my letters dated the 1st, 3rd, 4th, 5th, 6th, etc.
[Amount] F
[Amount] F
I have received yours dated the 3rd inst.
109
...credited to your account, subject to reserve.
Included herein are bills amounting to F 8,739.16 (see the attached schedule below), for which credit has been passed and receipt acknowledged.
I have the honor to remain,
Dr. [Debit] / Cr. [Credit]
Per Procuration — Special
The Director,
[Signature]
Schedule.
EXCHANGE
Terms
INTEREST
No.
Amounts.
Value.
Places of Payment.
Due Dates.
Rate. Proceeds.
at 6% p.a.
Running
R. Chateauneuf
[Charges] Paid
At Sight
Cognac
Surgerès
Jarnac
Cognac
Jarnac
Cognac