Jean-Jacques was considered as one of the most skillful founders of France. In 1669, he became "Master of the foundries" (Commissaire des Fontes) at Douai. He also established other foundries in Besançon, Breisach and Pinerolo. His work was integral part of the plan established by Louvois in 1666 to have the army and artillery reorganized.
His brother Jean-Balthasar was rather involved with the founding of statues. He famously founded the statue of Louis XIV then located in the Place Vendôme, in December 1692, in a single piece, something never achieved before. The statue was destroyed during the French Revolution on the 10th of August, 1792.
Jean-Jacques met with trouble when some of his guns burst in 1694. He was then replaced by his brother Jean-Balthasar as Commissaire des Fontes at Douai.
The two brothers had a great influence on cannon founding techniques in France, and made thousands of artillery pieces.
The technology they employed, involving the founding of cannons around a plaster core, was superseded by the De Vallière system in 1732.
Media related to Keller cannon at Wikimedia Commons
- "Jean- Jacques Keller, his older brother, the most skillful cannon founder in the service of France" in One Hundred Years at V.M.I. - Page 263 by William Couper - 
- Gunfounding and Gunfounders by Arthur Norris Kennard, p.96-97
- The History of Paris, from the Earliest Period to the Present p.27
- Galignani's New Paris Guide By A. and W. Galignani p.193