To implement this design, I came up with an idea of a ring PCB that would hold 3 side-mounted LEDs on the inner side and castellated holes on the outer side to connect all PCBs together and to drive signals. Designing this PCB I forgot about two very important things. 

The first one is that the milling tool that cuts a PCB has a big radius, which is kinda catastrophic for such small holes and slots as in my design.

And a second one - gold plating also adds extra thickness. As a result, my LEDs didn't fit at all. The gap between PCB and LED was HUGE! You can clearly see that in the next photo where I tried to solder them. 

At the same time for the first prototype, I made acrylic parts using a CNC machine. It wasn't a good idea. Probably because of the milling cutter, settings, or small dimensions, engraving on acrylics looks very rough. And one side of that acrylic is with antiglare effect. So.......it is unlikely that I will see the last symbol in a bunch. (proper testing still needed)  

Four disks stacked on top of each other:

To fit an acrylic disk to PCB with "mounted" LEDs I had to use a scalpel to cut small slots in the disk.

As a result, I got a lot of sidelights that would also light up the previous and next symbols in the assembly. Although, honestly speaking, it happened not only because of these cut slots, but also due to LEDs being put not deep enough into PCB. To solve all that I should have made two different versions of the same board with slightly shifted LEDs, which means that the next board in the assembly would cover the previous one and prevent from undesirable light. 

As for the first iteration, I'd count this result as a small success, mostly to cheer myself a little bit up :)

Before designing the new version of PCBs still have a lot to test. Mostly will order central pieces with laser engraving and will try different materials. Also want to assemble everything together and put it into a test tube that I'm using as an enclosure. 

Will keep you posted.