Need Help with Voltage for Integrated

I recently acquired an Arcam FMJ 18 (nice little unit, BTW), plugged it into my standard (120/240v) power outlet and began using it without problem. Subsequently, I saw printing  on the back of the unit that indicated 220/240v. There is not (contrary to the manual) a switchable power button on the back. My working hypothesis is that either (a) the printing is erroneous and the unit is 120v, or (b) I'm using the wrong power supply and will fry the unit. FWIW, the previous owner, who was something of a stroke, told me that he had used the unit with standard 120v power with no issue. Should I be concerned here?

Per the downloadable users manual Version at the Arcam site,the voltage is changeable via a fuse internal to the amp. Have you popped the top and checked the fuse value/location/etc.? Might be obvious once you get your eyes on it. Or not.....

BTW, per a review I read, it looks like the may have made the voltage change switchable via an external switch at some point during the production cycle. But the users manual version at the Arcam site does not show an external switch.

Link to users manual:

Make sure you have the correct amperage fuse!

The current probably halves or doubles depending on location.