Greetings Andy: When George Frow and I did the first book in 1976 printing costs were so high that much was left out and a great many expensive photos were eliminated. Such was the more fine dating of early models. Luckily we now have the Internet with the ability to share information instantly. The Triumph appears to have made the transition from Spring Motor around serial 30000. I say around because I have seen a Spring Motor with a serial of 29906 and a Triumph A with a serial of 29319. These all have the last patent date as May 31, 1898. You won't see the last patent date change to November 17, 1903 until around serial number 40000. Your machine is very likely made in 1901 since the serial is just 31700. I hope that helps. Al
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