I use a multimeter that includes a thermocouple probe for taking temperatures. That's what I use for checking my wax iron temp (I have a Toko iron too). When I check it with the thermocouple, it's always around 4 degrees C under the temp indicated on the iron.
Concerning your iron not getting hot enough: Check the voltage rating on the iron. It's on the "base" end of the iron imprinted in the plastic. A US iron will be rated 120v. A 'euro iron will be rated 220v or 240v.
To use a 120v iron in Europe, you'll need a plug adapter and a transformer.
Similar deal if you actually have a 220v 'euro iron that you want to use in the US... BUT: that could be tricky for a high wattage thing like an iron and could mean you have to use the iron+adapter+transformer via an outlet rated for 20 amps. Even then, it may still under-perform.
It's also possible your iron was assembled incorrectly. Basically, they may have mistakenly mated a 'euro 220v iron to a US cord assembly. That would definitely explain why your iron seems to generate about half the heat that it should. It can happen.
Lastly, if you're positive you have an iron with the right rated voltage for the country you're using it in then use a multimeter to check the voltage at the outlet, as the voltage may be way too low. I've been in hotels/hostels that had power so bad that my wax iron couldn't reach temp as usual.
