How can I tell whether a Mega is R1, R2 or R3?

Hello, I want to buy a Mega 2560 R3. How can I tell if it is R1, R2 or R3?

R3 has an ATmega16U2 for the USB-to-serial chip. Adafruit sells the legit Mega 2560 in the USA. arduino.org is selling another new variant with the reset button in the upper left corner instead of in the traditional spot next to the main processor's ICSP header. If you are considering buying a Mega 2560 online from some place like Amazon, eBay, or Aliexpress, they are often listed as "R3" regardless of whether they have ATmega16U2 or CH340G or some other chips or specifications, and often regardless of what is shown in the listing's pictures or technical details, so you have to just take what you are shipped and like it.

The problem is that I am not in the US right now. In my city, there are only two stores that sell the product. RS and a very small shop. The latter is selling the Mega at about 1/3 the original. So, it may not be original. As for RS, there is no indication of whether the one they are selling is R3. I talked to two persons working there. They have no idea about the revision number but one of them said that it is probably R3. Is there a way to tell from the box? If not, once I have received the product, how can I tell if it is R3 or not? Don't know if ATmega16U2 is written on the board.

Just use a magnifying glass and look at the chip close to the USB port, see if it is ATmega16U2. Why is it important to be R3?

dmjlambert:
Just use a magnifying glass and look at the chip close to the USB port, see if it is ATmega16U2. Why is it important to be R3?

I read that some shields are only compatible with R3.

Too bad Adafruit does not ship Arduino outside the US. If Arduino and Genuino boards are the same thing, why Arduino is for USA only?

There is a legal dispute going on with arduino.cc and arduino.org, so they may be constrained on where they ship.

I don’t know about the shield thing. But then I don’t think shields are a good idea anyway. They shield you from knowledge you would otherwise gain from connecting your own components and modules.

newto_arduino:
Too bad Adafruit does not ship Arduino outside the US. If Arduino and Genuino boards are the same thing, why Arduino is for USA only?

Arduino.cc (us) owns the Arduino trademark in the USA. Arduino.org (them) owns the Arduino trademark in Italy (and thus the European Union?). That is why Arduino.cc has to sell under the Genuino name in Europe.

Since Adafruit ships and distributes almost everywhere, it seems like it would be a good idea if they also used a Genuino silk screen when producing some of the boards. That way they could just pick the proper board and ship according to destination address.