I had a choice of making it in plaster of Paris and then sending it to them to be scanned for printing, or getting it built up in CAD by a third party and doing it using the computer. Because of the repeating elements, I decided it would be better to do it using digital technology, and so I worked with another company to realise it in 3d.
It was a weird process. Apart from the 2d layout above, it was all in my head, and I was having to try and explain to someone else what shape it should be, and what measurements. So I decided the easiest thing to do would be to send them sketches of each component and we could discuss them as they were extruded on the computer...
It was a complicated process, but it worked! In the end, Renishaw printed the prototype and it looked not far off the original. Some things we'd changed because of tolerances of the material or the printing process.
It's now installed at the Station and every time I pass it there are pennies in the holders, so people are clearly using it all the time!