How did this work on the old typewriters? If you have ever looked closely at most antique machines, you can see that each striker has the upper case and lower case version of each key - which version is typed depends on whether you are holding the Shift key.
But some typewriters had three markings - the upper case key (for instance, N) the lower case key (n) and a symbol or number - in this case, the colon or : key. For the capital N, hold down the CAP (capital) key. For the symbol, hold down the FIG (for figure) key.
Some keys had no letters but three symbols -
Of course, some typewriters used the opposite approach - the same symbol would be typed no matter where the typewriter's carriage was held. In that case, only one symbol was needed on the key -
The triple strikers can make for some fun keys - be sure to visit www.hautekeys.etsy.com to see them all!