According to David Doyles' book, An M51A2 W/W has a value of between 1800. and 29k for a pristine...not so rare. An 817 W/W, 1500 to around 29k..again, not so rare. A 929A1 WO/W, 3500 to around 36k, a bit more rare to see. There is also the M930 W/W...same as the 929, but with a winch.