Warren, Yes, GBA has 2 type of double-bit models. The one you are describing is the 490-2. It has the 2 different grinds. It also has a 31" handle. The one I have is a 490-1 with the 25" handle. I need to set up a target for it before I can go Viking.

Here is GBA's write up on the 490-1 throwing ax:
The Gränsfors Double Bit Axe is based on the North American working axes, but has been modified for use in axe throwing. Both edges are identical and the centre of gravity and handle are carefully positioned so that the axe rotates well in flight. The dimensions and design of the axe comply with the rules for axe throwing.