Motoplat is a Spanish made magneto used on some Sachs 504 moped motors. It is most easily spotted by the red coil under the tank, and the gold colored flywheel. Sachs appeared to use these ignitions on a good portion of thier 504 motors rather then the german bosch. They do appear to work well. Some believe they are prone to condensor failure a bit earlier then the other system, but this is easily fixed and parts are still availiable.
It is of importance to note that the stator and flywheels are not interchangeable with the other system, but you can swap out both and convert one from another. The bikes however , are wired differently and will require you reading the wiring diagrams for each and figuring out the wiring, as the systems are entirely different on the bike as well.
<http://www.mopedarmy.com/wiki/Image:3motoplat.jpg> for a diagram of a motoplat iggy bike.