The resistance of 23 Ohms is correct for the 4001G, even says so on the Coles site. I reckon that the actual impedance of the 4001G is in excess of 23 Ohms.
The 16 Ohm impedance rating is probably because the Coles (originally STC) may have been used on early Hi Fi speaker systems of 16 Ohm nominal impedance.
http://www.coleselectroacoustics.com.../super-tweeter