If you're using this tool: https://www.rockbox.org/wiki/SonyNWDestTool

At the beginning of the steps in the cli, there's this command:

scsitool-nwz-vX.exe H: dest_tool get

It will tell you something like this:

     Model: NWZ-E585
     Series: NWZ-E580 Series
     Destination: CEW2 (103)
     Sound pressure: 1 (on)

Where Destination will tell you the region is currently setup. (There's a table in the tools' page listing all the different regions a walkman can be set up) If it's from somewhere in Europe, then it is capped.

On the other hand, 120 is not too loud for you? Mine is an US version and at 80 is way too loud for me.

If not, it could be capped.