Mustard is of course very important in French cuisine, and this was the best mustard, from Paris' premier supplier, Julien Damoy. The design celebrates the medals won in 1885, so it can be confidently dated  from 1885 to the 1890s.
 
This gorgeous collectible little pot measures 3.75" tall, these are scarce finds due to the exclusivity of the Damoy store in the 19th century.