From the project page (accessed 2019-09-03):
Coinage of the Roman Republic Online (CRRO) aims to provide in effect an online version of Michael Crawford's 1974 publication Roman Republican Coinage (RRC), which is still the primary typology used for the identification of Roman Republican coin types. Since its publication in 1974 there have been significant revisions to the dating of the series following the discovery of new hoards, but no attempt has been made to reflect these or make any other amendments to the published typology at this stage. The descriptions for these coins are based on the typology set out in RRC, but have been modified to meet the standards of the British Museum’s collection management system. Additional types not in the British Museum’s collection were added to this database by Richard Witschonke of the ANS.