Indeed, there´s no info about the voltage of the relais. Here´s a way to measure the voltage for the coil: try to solder a pot instead of a relais-coil. Have look in the datasheet for the coil resistance of these relais and dial that resistance in with your pot. Now the right current for the 24V relais should flow if it is the right coil-voltage. Hence you should measure 24V. If not dial in the coile resistance of the 12V version of that relais and check this again.... Hope that helps.