The “green cassettes” by the Hungarian paleontologists Hantken and Madarász, are 19th century exhibition slides containing specimens of Nummulitoidea collected from some famous Paleogene successions of the Tethys. These particular slides, due to their meticulous preparation, distinctiveness and uniqueness, can be considered “iconic”. The Giovanni Capellini Geological Museum at the University of Bologna likely holds the largest collection (114 slides subdivided into six groups) of “green cassettes” outside Hungary. Here we reconstruct the history of this collection and its relationship to other similar collections, and provide the taxonomic revision of the specimens, which identified 32 species of Nummulites, 5 of Assilina, and a Pellatispira. Also, the topotypes of five species of Nummulites were recognized. Special attention was paid to the specimens of species established by Hantken and Madarász to evaluate their validity. Specifically, we found that the specimens of Nummulites baconica and Nummulites vicenzaensis can be assigned to Nummulites gallensis and Nummulites fabianii, respectively, while the microspheric specimens of Nummulites hungarica and the megalospheric ones of Nummulites d’Archiaci can be attributed to Nummulites aturicus. In contrast, the validity of the species Nummulites kovacsiensis, Nummulites subplanulatus, and Pellatispira madaraszi was confirmed, with the former being a senior synonym of N. boulangeri Schaub 1981. The specimens of these species would therefore represent syntypes.