'Tis indeed an F3 shock.

The added bonuses over the stock SP shock are stronger internal damping, a lightweight aluminium body and ride height adjustability. The actual damper valve is the same as an NSR, but there's nothing wrong with that.

The fact that it has a valve in the reservoir means that it's been rebuilt. They came from the factory fully charged and "non-rebuildable".

I have the very same shock on both my NSR300 and NRS250. They work great. I have another in my box upstair, but it's missing the top mounting piece.

The stock NSR SP shock can be rebuil;t to the same spec as the F3, and then recharged with nitrogen in the same manner as the F3 shock shown in the picture by fitting a valve. Just for your info, they're charged at 150psi.