[Left side]
[Emblem of Nantes]
LAN 1788
LE I3ME DU REGNE DE
LOUIS XVI
LE BIENFAISANT
CE MONUMENT FUT TERMIN
LOUIS JEAN MARIE DE BOURBON
DUC DE PENTHIEVRE GOUVERNEUR
LE COMTE DE THIARS COMMANDANT
LE DUC DE CERESTE DE BRANCAS
GOUVERNEURDES VILLESET
CHATEAUDENANTES
DE BERTRANDE
DE MOLLEVILLE INTENDAN

[Right side]
[Coat of arms of Jean-Baptiste Bertrand-Geslin]
ETOIENT POURLORS MAIRE
MESSIRE PIERRE RICHARD DE LA PERVANCHERE
ECHEVINS
RENE DREUX SOUS MAIRE
JEAN CHARLES GERBIER
JACQUES BODIN DESPLANTES
RENE GESLIN
SIMEON PLUMARD DERIEUX
JEAN JACQUES URBAIN MESLE PROCUREUR DU ROY SINDIC
PIERRE CUILLAUME HENRY
GIRAUD DUPLESSIS
SUR LES DESSINS
DE MATHURIN CRUCY ARCHITEC ET VOYER DENANTES

The signs are on the façade of the Théâtre Graslin, Nantes’ opera house. The building erected in 1788 was designed by Mathurin Crucy.
Jean-Joseph-Louis Graslin, after whom the building is named, was a tax collector who worked to expand the city center of Nantes.
The building is designated as a French historical heritage site

The right part of the sign is shown in the following picture Click for a larger image
The opera building was photographed on the same day Click for a larger image

Translation of the text on the sign:
[Left side]
[Emblem of Nantes]
LAN 1788
THE 13TH OF THE REIGN OF
LOUIS XVI
THE BENEFICIAL
THIS MONUMENT WAS COMPLETED
LOUIS JEAN MARIE DE BOURBON
DUKE OF PENTHIEVRE GOVERNOR
THE COUNT OF THIARS COMMANDER
THE DUKE OF CERESTE DE BRANCAS
GOVERNOR OF CITIESET
CHATAUDENANTES
BY BERTRANDE
DE MOLLEVILLE INTENDAN

[Right side]
[Coat of arms of Jean-Baptiste Bertrand-Geslin]
ETOIENT POURLORS MAYOR
MESSIRE PIERRE RICHARD DE LA PERVANCHERE
ALDERMEN
RENE DREUX UNDER MAYOR
JEAN CHARLES GERBIER
JACQUES BODIN DESPLANTES
RENE GESLIN
SIMEON PLUMARD DERIEUX
JEAN JACQUES URBAIN MESLE PROSECUTOR OF ROY SINDIC
PIERRE CUILLAUME HENRY
GIRAUD DUPLESSIS
ON THE DRAWINGS
BY MATHURIN CRUCY ARCHITEC AND VOYER DENANTES