Are you sure its not a W11B. I think B was the last unit before the new series came out. They were a sweet machine for its size. 70 HP case 4-390 engine and a one yard bucket, fast and with good breakout force almost 10,000 lbs and 4,200 on the lift while clearing a 10' sideboard on a dump truck. Turbocharger, cab unit, 4x1 bucket, extra weight package, suspension seat, were the main optional equipment. I think the mid 80's was the last built so your looking over twenty years old. They filled a void for contractors, cities, towns that wanted a small articulated machine.