Yeah ok, then there is no resistor. Probably 4 LED in series. Uncommon, because a resistor, or the voltage drop of a current regulator, will take you to uncommon voltages.
But you also see that 12V will kill your element. And you also see that between 500mA and death, there is a distance of ~0.2V. So you do not want to just adjust a voltage source source to a voltage that initially gives you 500mA. Something may drift, and gone it is.
With the 6 Ohm, you will be fine.