Chaplain was born in 1839. In 1863, at the age of 24, he won the Prix de Rome. He returned to Paris five years later and almost immediately found success in the Salons of 1870 and 1872. From then on he continued to gain recognition and honors. By 1877 he was named the official medallist of the French government; in 1878 he was a chevalier of the Legion of Honor; and in 1881 was given the seat at the Académie des Beaux Arts.
Chaplain was responsible for the official portraits of every president of the French Republic from Edme Patrice Mac-Mahon in 1877 to Émile Loubet in 1899. He also received a commission to engrave the gold coinage of France. When Czar Nicholas and his wife, Alexandria, came from Russia to visit Paris in 1869, Chaplain created a gold medal to commemorate the occasion, and this magnificent medal was considered to be one of the very finest ever made.
Despite his success in medal making, Chaplain's cast portrait medals are considered his greatest artistic achievement. He developed an accurate and penetrating style of portraiture which stood out from its metallic background and straightforward composition.
One of Chaplain's projects was a series of twenty or so cast medals representing prominent artists and creators of his day. He began this series with a portrait of the medallist Auguste Barre in 1879.
Chaplain opened the way for medallic art experimentation as one of the first artists to produce models for cast medals that were equally effective when reduced in size and struck. Traditional techniques were deviated from by other artists and by the end of the 1800s, medallic art technique had transformed into a much more personal touch, unique to the artist, which allowed for a broader use of their talents.