There's quite a good clue to there being four levers, but I'll leave that as an exercise for the student.
Yeah, it could easily be only 3 heights. I keep looking for the 'Enhance' button on Photoshop but I still haven't found it.
Thinking on you would have to buy the keys wouldn’t you as you wouldn’t know which of the 81 to make
I don't think it's giving much away to say that 5 minutes in B&Q would let you sight-read most of the actual combos.