What does the nameplate say, exactly?
NEMA standards generally specift a 10% tolerance, based upon the nameplate rating. That's why there are so many different ratings found on nameplates.
If the nameplate says '208,' then that appliance can be used with any voltage between 188v and 228v, actual measured voltage.
Another approach is to look the implications of Ohm's law. With resistance, voltage variations have an effect that is "squared." That is, doubling the voltage results in four times the heat being produced. That toaster will put out a hell of a lot more heat at 240 than it will at 208. Sounds like a recipe for burnt toast ...