This was one of my few prizes from an overall mediocre NAWCC National Convention. The first run of 1872 model Waltham movements ran from SN 600,001 to 600,500, and were 16j gilt Am'n grade.
Mine is SN 600,165, meaning that by the serial number it was the 165th 1872 model movement. I've seen and held lower numbers than this, but I was happy to find this one and the price was right on it.
I also have a couple of examples from the second run of 1872 model movements. I'd really like to add an example of the third run to my collection, but I know that one of those won't come cheaply.