These are professionally prepared 'Working Cards'—as opposed to 'Playing Cards'. Conceived and designed by busy.cards ®, and printed in the UK by specialists, these cards come in a variety of sets—all named after various rivers. (The various river-labels are chosen at random—often because of the convenience of their short length, eg: [keer.busy.cards]. The rivers Keer and Kent are both in Cumbria, UK)
The Kent Set of busy.cards is a pack of 56 cards covering the most difficult times-table factors 'in reverse'. (The two and ten times tables are not listed.)