there are two versions:

• R1 - has an external antenna and the terminal pins are all black
• R2 - has an internal antenna and the terminal pins for mains and load are black, for switch they're grey

till now, I have some of the R1 boxes. The external antenna is useful for placing in a metal enclosure (for example in my case in the switchboard/fuse box, where my Sonoff Mini controls the floor lights an the antenna cable is routed to outside)