I finished the counter mechanism, I doubled the size of the wheels to make them easier to run and I added a detent mechanism to ensure that the smallest wheel falls into place and it also stops it spinning wildly. (svg here)
The geneva mechanism was rebuilt using a layer of 2mm ply, this allowed the two different gears to sit half a step out of sync with each other and eliminates any clashing as the gears rotate.
The detent mechanism gave me a few headaches, typically these mechanisms usually look like a rounded ratchet. The rounded end allows the lever to slide in either direction. The trouble with laser cutting and wood is that the edges are a little bit rough and I really struggled to make this design work in the reverse direction.
To solve the problem I got thinking laterally, I put some 0.8mm ply in side ways to press against the sides of the decagon. I put in 2 bars to create even pressure on both sides of the wheel. As the decagon rotates it flexes the two bars outwards and that helps it bump over into the next detent. The rough side of the decagon rubs against the smooth surface of the 0.8mm ply and there is no sticking.