If it's not printed on the part, you'll need to consult a data sheet. Typically, the switching power at DC will be considerably lower, at worst case, the switch can't safely interrupt DC current of some amount at all. That's due to the fact, that an AC switching arc will safely extinguish at the next current zero-crossing. If a DC arc won't, it can destroy the switch.
In general most switches have the same current rating at 24V DC as 230V AC. Look at electronic catalogues for similar switches and see how their ratings change.
Frank