Athlon 64 4200+ pictured@ 2005/03/07
This CPU is actually clocked at 2600MHz just the same as the FX55 but in the case of Athlon 64 4200+ the multiplier is locked higher. The 4200+ has 1MB of cache built on 90 nanometre marchitecture and works with 1.4 volts.
This looks like a San Diego core to us as it has SSE3 and it is built on 90 nanometre marchitecture.
This means that FX57 new AMD gaming CPU that should rock at 2.8GHz and have multipliers completely unlocked is close to its release. Maybe CeBIT? It would not be the first time. Helas.