The Saracen Roller lock mechanism is often found in older type double glazing windows with shootbolt technology.The rod in this gearbox mechanism has a long thread all the way up the shaft.
Gearbox mechanism Only (rods can be bought separately).
Rollerlock systems consist of rods and a unique central gearbox mechanism. The rods fit into the the gearbox with a threaded fitting using a twist motion. Shootbolt rods are available in four lengths and are simple to connect to the gearbox.
This is what the actual lock looks like when in position in your window.
To remove the lock you need to take off the face plate, Remove the handle and the end guides that the shootbolts go through at the end of the window sash. You then put the handle spindle back in and turn the handle including the back plate in an anti clockwise direction. This should wind the shootbolts out so you can replace the gearbox.