Physically it's the same GPU with a different name, with the same specifications, clock speeds, performance, and they are all derived from the Radeon HD 7770's GPU, so it's not uncommon for the displayed name to differ, it's a bad decision the driver development team makes, but it is the same card, so one is not "better" than the other.
Also, going by the fact the R7 450 is almost 4 years old, I'm guessing that PC is used, and if it's new then someone conned you.