Just saw this article in Hemmings and thought of Marty. A driver's signaling ring, circa 1920s, and worn over the driving glove to signal other motorists. One of the first motorist turn-signal devices invented.
Don't know if it would clash with Sandy's jewelry (I believe her to be more elegantly understated), but pretty spiffy none-the-less. I was intrigued with the engraving along the band -
https://www.hemmings.com/blog/?p=897751
Maybe not as cool as the Green Lantern's ring, but it appeared some 20 years earlier!
