I don't think there is such thing as an MP4-12C MSO..
There was an MP4-12C Project Alpha, which showcased the new exterior options for the MP4-12C, and that led to new MSO (McLaren Special Operations) factory options for the base 2013 model.
So I think this car is a base MP4-12C with some MSO options, like the black roof and rear. It still misses some other MSO upgrades, such as the front bumper and the air vents in the wheel arches.
It's like the carbon rear panel and skirt options for the Ferrari 458. The same base model, with some factory exterior upgrades, not a whole different car.
I think that's what Xx_in_your_dream_xX is trying to say.