the appliance is a heater pot for melting solder
Since this is a heating appliance designed to "Plug in" in a country that (officially) uses 230 V AC as their domestic supply, it is unlikely that the current drawn on 230 V will exceed 10 A. (The "name-plate" should indicate this and the small devices that I find listed on Ebay are rated at only 150 W - 652 mA)
(If it is one of these small devices, I note that 120 V versions [SJ-350A] are available for $19 - with free shipping !!!)
Does this device have a 240 V NEMA Plug already connected?
If not, to operate it you will need to cut off the existing plug and connect it to a 240 V supply (L1, L2 and Earth - the "Neutral" being unnecessary in this case) via a suitable NEMA Plug and Socket combination of at least the rating of the appliance and its "cord". (This should not be difficult to arrange, since the lowest rated NEMA types are 15 A!)
You could install a 2 pole switch in association with this socket, or just unplug it each time that you wish to turn it off.
The colour code of the device supply lead will probably be Brown (L1), Blue ("Neutral" in 230 V countries but L2 in your case) and Green or Green/Yellow (Earth)
If there is a switch on the appliance it will work as normal but, of course there will be two 120 V supplies up to this switch and the heating element as long as the device is "plugged in". In this it is in no way different to a 120 V device plugged in and using a switch to "operate" it, except that, in this case, there is no connection to the "Neutral" at the premises.