It is a gear driven, with six speeds.
Speeds are selected by moving the lever to the side, or up and down.
This is the lower section of the gear box, it has two speeds for the upper and lower range of speeds.
This is the upper section, it has three speeds.
Here is a better pic of the assembly (The pic is from the back, the right side is up, and left is down). The motor input is where the pipe is coming out the left hand side of the pic. The box area under the strap, is the oil pan, and pump. On the right, you can see the shift shaft. It is connected to the lever on the front. Rotation makes the rearward shift arm to go up and down, it controls the 3 speed box. Just forward of it, you can see the other shifter, it is controlled by the rid going forward and back (In and out), it controls the two speed section.