Numismatica Ars Classica One of Europe's top numismatic firms
Classical Numismatic Group, Inc. A leading U.S. ancient coin dealer
Rasiel Suarez The author's services web page

Principal online resources used:

Coinvac.com The largest database of Roman Imperial coins on the net (built for this project)
The Tantalus Coin Registry A publicly accessible coin registry
CoinArchives.com Another massive database of closed auctions
WildWinds A popular database built by the late Dave Surber
Dirty Old Coins Comprising the 10,000 most popular Roman coins

Coin dealers and numismatists allowing use of their photos include CNG, Ancientauctionhouse.com, Dmitry Markov, Münzen & Medaillen, Numismatik Lanz, BeastCoins, Ancient Treasures, Ancient Imports, David Connors, Wayne Sayles, Roman Lode, Sotheby's, HD Rauch, Rudolf Künker, Tkalec, Spink & Sons, Astarte SA, Alex Fishman, Hess-Divo, Leu/LHS, Byzantium Coins, UBS Gold & Numismatics, Ed Dopierala, Brent Upchurch, Freeman & Sear, Kevin Rankin, Auktionshaus Meister & Sonntag, Rutten & Wieland, Helios Numismatik, Stack's, Dr. Michael Brandt and Dr. Busso Peus Nachfolger.

Principal programmers: Dan Kellem, David Karn, Tomaz Miholic, Agustin Esmoris, Michael Gershenzon & Jeff Jansen

Several non-coin photographers allowed use of their work. Thanks go to William Storage, Justin D. Paola, Ronan Guilloux, Mary-Lan Nguyen, Christiane Casale, Wilson Delgado and Guitty Azarpay.