- " "Hey, kid," the old guy called as Marty walked past, "can you thumb a hundred bucks to help save the clock tower?" He held out a silver box with the inscription "Portable Thumb Unit". / Marty hesitated. / "It's an important piece of history," the other guy added earnestly. The circular name patch over his pocket said his name was "Terry". "
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 49)
A portable thumb unit was a rectangular-shaped handheld electronic wireless device with fingerprint scanning technology, used in 2015 to collect donations and other funds where a person was unable to access a teller.
- In 2015, as well as prior years, rectangular-shaped handheld electronic tablets with fingerprint scanners are commonplace, and are used to make payments using fingerprints.
- Back to the Future Part II
- Back to the Future Part II novelization (First identified as Portable Thumb Unit)
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