Patent No. 2,646,717: The Nomoscope. “Device for the Identification of Documents or Printed Matter,” aka the dollar bill changing machine.” Atdinner parties my inventor papa wouldquip, “Yes, that’s right, I invented the first machine that gave changefor a dollar bill and never gota nickel from it.”

The story of the ill-fated “Nomoscope” is told through a series of letters and affidavits to and from attorneys, and is much more complicated than my father’s glum one-line party quip suggests. In...