The manual for the meter says "Maximum allowable pressure drop: 600mv", which implies a 1 ohm shunt for the 600 mA and lower ranges. The accuracy spec's are rather odd, but my guess is that the accuracy for the 60 mA and 600 mA ranges is untrimmed (other than main voltage calibration), whereas that for the two low ranges is trimmed in the required amplifier for the shunt.

 

You guys are ridiculously helpful - thank you all so much for your inputs