But there is a coil resistance of 1K, so Ohms law would indicate a voltage of 2.3 Volts.
But, since it list an operating current instead of a voltage, it might be intended for a non-standard application where the relay coil is in series with something else.
2.3mA would be the minimum current, which may not give very fast operation.
I'd consider them to be 5V or possibly down to 3.3V
At 5V the power dissipation is only 25mW, negligible for the size of the coils.
(or around 11mW at 3.3V).