The newer style magneto comes with only two wires, a black and a blue. This newer generation of magneto has the white wire omitted with the black wire soldered to the core. The core has been epoxied to help reduce fatigue to the ground wire and also has a jumper wire to ground. Additionally, the frames appears to be of better quality as well.
Testing this two wire magneto is really simple with the use of an ohm meter. Specs and testing are as follows:
Ohm meter set to 2000K ohms. Red (+) on the blue magneto wire / Black (-) on the magneto black wire. Reading should be around 325 ohms. If you switch wires the reading should be the same.
With your ohm meter still set to 2000K ohms, put the Red (+) on the magneto black wire and the Black (-) to your motor case or magneto frame. The reading should be 0.3 which means you have a good contact ground. If your magneto meets these specs then you have a good magneto.
Falling below 315 ohms is a sign of a weak magneto or one that is cheaply made. Ideally if you can get in the 340 range then you have a hot magneto. Be aware there are magnetos that are being sold as a super mag, they look bigger , wires are red and black and the tape is a bright white. These magnetos are nothing fancy and do not come close to the specification of a genuine Roo magneto. Ohm testing is the only way to know the true resistance.