P25's were not sold without tonearms, so someone took off the original RB600 and switched it for the Clearaudio. I don't know if it's a proper fitment as I don't know if a Cleearaudio arm uses the same mounting point as the Rega arm.
The Exact 2 cartridge is the top of the Rega moving magnet food chain. I used to have an original Eaxact and thought it was a very livvely and dynamic cartridge. I had it mounted on an RB600, but eventually sold it when I sold the RB600 as well.