Lancashire & Yorkshire Railway Tyers Co-operative Permissive Block Instrument. A magnificent example with upper, 8 segment dial showing 'Train On Line; Line Blocked; Line Clear; then numbers 2 to 6 in individual segments. Below this top dial and above the central tapper & commutator is a crescent shaped window with a brass surround, indicating 'Train On and Permissive; Lines Clear and Trains Off'. The case is clearly stamped 'LYR' on the top. Excellent condition throughout.