The item was described as 'Arduino Mega ATmega2560'
Most likely it is a clone of the original Mega with an Atmega2560 instead of an Atmega1280.
I have personally sold a few of these, but I believe I make it clear enough that it is a clone that has the Atmega1280 replaced with a 2560. Unfortunately not all sellers explain that well enough. As far as I know, any original Arduino Mega with an Atemega2560 is a clone.
With that being said, it really doesn't matter (unless you require the new USB interface) if you have the new one or a clone that is upgraded. The Atmega2560 is officially supported now even though it still can not be fully utilized (certain factors may make this statement false). As long has you have the latest bootloader installed you should be able to use it as if it was the new Mega2560.