A total of 5 small boards are required for having a normal till with a lid, and the German narrow till (the "high edge").
For the "high edge" I was able to rip a board down the middle, and it gave me close to the dimensions that I had imagined while considering the build. The vertical part of it is 4 cm, and the horizontal part i.e. the bottom is 3 cm. This gives an interior of the "high edge" of 3 x 3 cm.
The front board of the normal till is 9 cm high, and the bottom board is 10.5 cm wide. The lid is 10 cm wide, and due to the canted ends, it protrudes approximately 1 cm over the vertical front. This is to make it easy to grip the lid with your fingers for opening.
The plan is to make two small dowel shaped protrusions on the back side of the lid, which shall fit into two corresponding holes in the sides of the chest. This way, the lid will be hinged by itself. I have seen this approach used on some old chests, and it is fairly simple to execute.
I have improved upon my planing stop. It used to be a loose piece of wood lying on the top of the workbench and touching the bulkhead. Occasionally it would fall down or move around which didn't make things easier.
I have tried to clamp the planing stop onto the bench, but then I risk hitting the clamp with either the plane or my hand. So I have moved away from this idea.
The latest fashion regarding planing stops is to tape them to the bench top and to the bulkhead. If you use yellow/black warning tape, you can give the whole set up a real quality look!
Look at the picture and judge for yourself, I am sure you will agree, that the same effect can not be had using blue masking tape or ordinary duct tape.
The next level will be to find a planing stop that is a little longer, to prevent my hand from hitting the bulkhead while planing. That would really take the set up to a higher level.
After planing all the boards needed, I tried to position them on one side of the chest, and it looked OK.
The next logical step is to cut the pieces to length and drill the holes for the hinged lid of the till. Then all should be ready for gluing up the carcase.
The improved (professional looking) planing stop.
Aerial view of the till and the "high edge"