All the variants :

Black wheeled Tank and grey wheeled Serpent (OER).

Brown wheeled Tank and green wheeled Serpent, that were sold in white head style boxes. Their origin is still unknown, but they could be found in Europe and in the US. The red-brown wheeled Serpent was known after, and is coming in the same box than the green wheeled Serpent. the funny thing is that even if it was the green Serpent that was seen on several catalogs, it is the red-brown that is on the box art.