The pictorial mark and letters (signature) on the bottom of this piece of Limoges porcelain whisper to us from across the centuries to tell us its origin.
The 'J.P.'-over-'L' is the artist designation. This one is the signature Jean Pouyat used on his undecorated white porcelain. The initials 'J.P.' over an 'L.' with the word 'France' underneath tells us that this plate originated in Limoges, a city in central France (that's what the "L" stands for).
That signature combined with the green wreath tells us that this piece is an authentic Limoges factory decorated piece.
Because the green wreath was the mark used around the middle part of the 1800's, we know that's when the piece was made.