Based on your reply I searched on Wikipedia. You are correct, 11/- = 11 shilling, 2/6 = 2 shilling & six pence; the "D" stands for pence, hence 6D = 6 pence. In the old days (pre-1970s) 12 pence = 1 shilling & 20 shillings = 1 pound which all went away when the Empire switched to a decimal based system. Coverting apples to oranges I get that a 6D chip is the same as a 50¢ chip [a fractional half].

I still welcome any additional insight/information.