[h2odragon]

Postal Pre-sort routines. Many years ago, when the most reliable way to get the real walk lists was to go to the local postmasters.

There was fairly cheap commercial options even then but that shop had a bad "dont buy what you can build" attitude combined with a maddening shyness about making any other use out of the things they'd built. Having written our own presort software, we couldn't then sell it or even open source it because that would be "a burden distracting from the core mission of the business."