norb:
The ridge is actually a good idea stops items rolling /sliding from one side to the other and getting stuck possibly under a pedal
Yep, Sed Ack 401 had a superb flat tray with decent lip all around, nothing would fall off.
Doncha just love how in many modern motors stuff rolls off the slippery as an ice rink semi curved centre and wedges itself in that most ideal of places to retrieve items from, between the bloody bonnet cover and the drivers seat 
not sure which is worse for this Scania or MAN.