I believe you are talking about the difference between the ash pan and the ash plate. This all comes down to money, I have used both and by far I prefer the version with the pan as is does a great job of preventing hot ash from blowing all over. Both versions have blades that sweep the ash out and are also used for air flow, the one with the ash pan is easier as you can actually make off where it is closed, half way and open all the way. You have to kind of guess with the one with the plate.
One-touch silver with plate
One-touch gold with the pan
This is what we call them in the states, I assume since you referred to it as a 57 cm you would be out of the states.
Again, my recommendation is if you have the extra money, get the Gold or the one with the ash pan.