At long last we have found a supplier of quality hand-made accurate current shunts. They are designed to work across a Digital Panel Meter on their 0 - 200mV range, i.e. the most common type. When set on this range the DPM will read the voltage drop across the shunt directly in amps. Strictly speaking, the 50A shunt will read under 5A of course.
The shunts are quite ruggedly made, however and will happily withstand up to 20% overload. To set up the DPM simply wire the appropriate decimal point to the meter board and connect the 0 - 200µV straight across the shunt inner screw terminals. At 50mV (for 5A) the meter should read 5.00A. The ‘A' annunciator must be wired up as well.