Six volt systems typically use primary windings in the coil of .6 to 2 ohms.
Twelve volt systems (with breaker points) tend to use the same coils with external resistors giving an additional 1.2 - 1.4 ohms in primary resistance.
Twelve volt systems with NO external resistor tend to use the same total primary resistance built into the coil-can. I.e. .6 - 1.8 ohms in the can plus 1.2 - 1.4 ohms external = 1.8 - 3.2 ohms total (and sometime higher).
12 volt breakerless systems often use "six volt" type coils with no external resistor.
1992 Subaru 12 volt breakerless: 2.4 ohms
NAPA IC-12 Echlin 2.1 ohms primary, 8.9 ohms secondary
NAPA IC-14 Echlin 3.25 ohms primary resistance (no external resistor used) $43.49 2010
A500 12 volt 2.6 ohms primary, 9.8 ohms secondary
no external resistor used.
Echlin 4.2 ohms, 4.82M secondary (no ext resistor)
John Deere 6 volt (as used on 430, 1010, etc.) 2.6 ohms prim, 7.12 secondary. Same coil used on Deere tractors with 12 volt systems with added resistor.
Hot Spark brand - HS06HEC - 12 volt HEI, CDI and electronic ignition systems requiring a coil with 0.6 Ohms primary resistance. 11.6 K ohms secondary. HEI, CDI and electronic ignition systems requiring a coil with 0.6 Ohms primary resistance. Can also be used as a 6-volt coil for many applications.
Mallory 29219, 12 volt coil - primary 1.4 ohms, secondary 9.8K ohms. 58K volts
Mallory 29217 12 volt breaker-point coil, primary 1.4 ohms, secondary 9.8K ohm, 58K volts, Accel coil for points, 1.4 ohms primary resistance, 9.2 k ohms secondary resistance, 42,000 volts maximum voltage
IC23 1.2 ohms mostly Mopar
ICR11 1.35 ohms rated. I checked and it reads 2.8 ohms.