this pattern echos the notation in britain before decimalisation, when amounts were written in some combination of pounds (£), shillings (s), and pence (d, for denarius). in that notation, amounts under a pound were notated only in shillings and pence: sixpence was written "-/6" or "-/6d", 2 shillings as "2/-" or "2s/-", 2 shillings and 6 pence as "2/6" or "2/6d", and so forth.