This Avocet espagnolette upvc window lock should have either Avocet or WMS printed into the rail, visible with the espagnolette upvc window lock fastened in situ.
To ensure that this is the part you require, we advise you to remove the UPVC window lock from your window and compare it to the photo provided here.
Please choose the correct Backset [A], Cam Height [B] and Rail Length [C], all explained in the introduction to espagnolette upvc window locks.
22mm backset option now discontinued. The 20mm or 25mm backset version could possibly be used with some modification of the handle position. Check that the frame will allow for a different backset before modifications are undertaken.