Early Acheulian & Developed OldowanB / i)peninj19
Biface/Handaxe. Peninj, West Natron, Tanzania (c. 1.3-1.5 MYA). A variant of the previous biface shapes, this biface appears to consist also of a mirror pair of curvilinear shapes on either side, but with a mirror symmetry of a rectilinear+natural shape at top and at bottom. As an aside, this piece is like a translation of the Oldowan pebble core with accidental diamond-shape in the center, described in the Oldowan Gallery.
Illustration © T. Wynn. T. Wynn. (1989). The Evolution of Spatial Competence. Urbana, IL: University of Illinois Press: fig. 19. (yellow highlight added)