I recently had my DVLA field test done at a local Specsavers. They offered a choice so I selected a nearby branch that had recently opened. They all offered different machines, and the one I chose had a Benson 9000.
It looked the same as the others I have used in the past, but in use was significantly different. Instead of the red light being fixed in the centre, at times it moved to the outside edges and corners which was a bit disconcerting at first.
On finishing the test, I mentioned this to the assistant and she said that it was a surprise to them as well. This raises the question of whether using such a machine makes a difference to the stringency of the test.
Anyone else come across this and what bearing does the type of machine have on the test results?