The origin of the Apennine Bench Formation (ABF) has been subject considerable speculation with early interpretations being basin ejecta and impact melt based on comparisons with the Maunder Formation of Mare Orientale. Indeed the terrain to the east of Rima Bradley and to the west of Montes Apenninus shows strong morphological similarities to the Maunder Formation and has been interpreted as probable Imbrium basin ejecta and impact melt. This basin ejecta view was largely superseded by a volcanic interpretation based on morphological and then morphological and geochemical criteria in the post-Apollo era. Samples recovered by the Apollo 15 astronauts were interpreted as being representative of the medium-K Fra Mauro which remote sensing data indicates forms the ABF. This reinterpretation placed the ABF in the unique position of being one of the largest non-mare areas of volcanism known, post-dating the Imbrium event by a mere 200 million years.