I doubt if your messing with it yourself grade 3 equipment is required.
But a grade 3 device is a high security one designed to detect if someone is trying to defeat it with a rouge magnet or one in the wrong location. There will be arrown on the case indicating where they need to line up and it wont have anything like the same tolerance of a grade 2 contact.
Id also tidy up your wires there is too much exposed