I wonder if the biscuits were a) the white (sometimes a bit brown in colour) 'hard-tack' which was a potato based biscuit made so that you could use them as axle stands when fixing a puncture. There was another that was a sort-of 'garibaldi' biscuit laced with raisins. This was identical in size to hard tack but known as BISCUITS AB for 'Arxe Blocking'. Then there was the holy grail of biscuits Oatmeal Blocks. These were about 2.5" round and 3/8" thick, wrapped in cellophane and came in a tin of 10 or individually wrapped. They were VERY expensive and something to die for - like eating the finest succulent steak! And made by Huntley and Palmer in Reading and not available outside the MoD. Yummmmmy