I found this in my iPhoto library this morning.
One of my earliest jobs as a Graphic Designer saw me as part of the team that designed the new street signage for the City of London. My job was to create a fool proof system of letter spacing so that whoever created a new sign they always had the same look and feel. I was 20 odd and this was before computers kicked to save the day. It consisted of a 4 bar system under each letter and the following letter would but up to one of the 4 steps of the bar, a bit like the old Letraset system but more complicated. As the relationship of each pair of letters differ and you have Upper and lowercase letters as well as numbers etc. It ended up with around 4,000 combinations. You would have to cross reference each pairing and see what the step number was to align it. We had sheets of words all over the studio for a month to check the system. It worked, it still works and they still use it as far as I know. Although it does look a little dated now and I would now open the spacing more.
I didn’t do the tag on this particular sign though, that’s a bit naff.