Old foreign toaster voltage?

https://imgur.com/a/fj7ZI

I've got an antique toaster from Prague that I would like to use in the US, and I'm concerned about the voltage. It's labeled 220V on the side as expected, but the box actually has a stamp that says "!120V" on it (I read once that apparently around the time this toaster was made, there were some 120V outlets there, but I can't find that anymore).

So, assuming it might be wired for 120V, how would I go about checking that?

And if it's not, what would happen if I plugged it in and turned it on?