Counterweight 1 : (Also called "Ballast") Weight used to supplement the weight of the machine in providing stability for lifting working loads and usually attached to rear of revolving upperstructure. (Spec 2C)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}