Medieval European Coinage has a decent section for Merovingian coins. I know ANS issued great catalogues for Pseudo Imperial coinage, Visigothic coinage, and Carolingian Coinage. They might have issued a volume for Merovingian coinage
I do not know of any. I have MEC but its not in any way comprehensive for Merovingian. If you find one I would love to know about it myself.
Roberts' "The Silver Coins of Medieval France" has some catalog space dedicated to Merovingian silvers, but of course nothing for the gold. The catalog is more useful for the later medieval stuff, including feudal coinage. I think a modern publication on early Medieval French coinage in the English language is sorely needed.
Here are a number on-line resources (some French some English) maybe some useful...and worth looking at the references mentioned by Markowitz and Yoon which might have some other relevant sources. Yoon, David. “Gateway to the World, Corner of Nowhere: Provence in the Merovingian Period”, ANS Magazine 15:2 (2016) Maurice Prou, Les monnaies mérovingiennes, Catalogue des monnaies françaises de la Bibliothèque Nationale (1896; reprinted in 1969 by Graz) Dickie, Douglas P., and R. D. Parrott. “MEROVINGIAN COINS IN THE COLLECTION OF THE AMERICAN NUMISMATIC SOCIETY.” Museum Notes (American Numismatic Society), vol. 4, 1950, pp. 91–96. Belfort, Auguste de. Description Generale des Monnaies Merovingiennes. Paris. (1892-95) CoinWeek Ancient Coin Series: The Merovingians – Coinage of the Do-Nothing Kings by Mike Markowitz Domenic Corrad, The Merovingian Coins Their Origins, Significance, and Purpose in Dating the Sutton Hoo Burial Alan M. Stahl, The Merovingian CA coinage of Austrasia Money and Coinage in the Middle Ages Edited by Rory Naismith
