According to Gruber, where the SCO monograms differ from the previous projects is that monograms have been organized hierarchically by Oliver Hoover. Unlike in PELLA and PCO, where a monogram usually has one SVG file (but may have more than one to illustrate slight variations in style), the Seleucid monograms have been grouped thematically by letters and general design motif.
More details on the Numishare site …