I was hosting a group of Japanese friends for a couple of days (these are the ones that bought my Dauphine race car).
One of the group is involved with the McLaren Trust in Japan and asked me to take him to a guy who lives not far from me who owns and works on several McLaren race cars.
So we were talking about all the in's and out's of McLarens (me trying to sound like I knew what I was talking about) when this guy points to a shelf in his workshop which was occupied by 3 or 4 gearboxes. I didn't recognize them at first but it turned out these were Dauphine gearboxes. This guy has a worldwide reputation for installing Hewland gears inside Dauphine cases for the formula junior race cars. He manages to get 4 speeds inside a standard 3 speed casing and ships them all around the world.
One of the Japanese guests then retold the story of the very last Mille Miglia (1957) where a Dauphine apparently competed with a 5 speed gearbox.
The McLaren guys then pulled this out of another shelf.
Its a genuine period 5 speed Dauphine box made by Colotti Francis. I didn't take a photo of the insides but the reverse gear was about 6mm thick. All the selector shafts and forks are housed on top of the box.
Obviously this one is set up for formula juniors with the selector facing the engine however you can see that they made provision in the casting for the selector to face the other way when used in a Dauphine.