This was the STAN system to measure the weight and centre of gravity of the aircraft. STAN stood for SumTotalAndNosegear IIRC
The system worked by measuring the oleo deflections on all three gears. The aircraft was taxied for a short distance with take-off flap set and then stopped and the switch was held on until the reading appeared. It was used to verify the loadsheet and was not very reliable. A similar system was used on some early B747Fs.
The scope for misloading on freight aircraft is quite great compared to passenger aircraft. Usually it's pallets loaded in an incorrect order - therefore total weight OK but c.g. out.