This is an antique, A. Lanternier, Limoges bread & butter plate.
This piece dates back to 1900, but Frederic Lanternier started the company in the 1870’s. In 1890 the son, A. Lanternier took over the business, thus the A in the maker’s mark.
I have four of these little plates for sale, individually. They are all in very good, used condition. Take a look at the photos and you will be able to see the dimensions, and get a good look at the plate.
If you have any questions, please e-mail.