Rear Brake Pressure Reducing Valve

Can anyone tell me on a MK3 with a single circuit brake setup what the valve at the back next to the RH displacer housing seen below does. Is it solely a pressure reducing valve or is it the type shown in the WM that has a little ball which travels up an incline to block fluid flow to the rear brakes on deceleration. As you can see this valve is nothing like either of the two types shown it the WM. Well my one anyway! Also it is set at a funny sideways angle not really best for fore and aft deceleration! Is it fitted incorrectly or is it purely a spring loaded peek pressure reducer of some kind where the fitted angle makes no difference?



I will be replacing the hoses and a couple of the lines and I do not want to pull it apart, as I have no spare or parts. If it is not fitted correctly I would like to rectify it obviously.

Thanks

Nick