A Hong Kong module, which looks to be a copy of a similar Swiss design, could be found in a number of digital watches in the 1980s and early 1990s — mostly as promotional/branding watches and have become quite collectable because of it.
The module itself, LCA164, has pretty much just one function. An analog LCD with seconds.
Pressing the single button on the right sets the time (slowly!) as the minute hand sweeps around. Some cases also have a small, recessed hole which can be accessed with a pin, but the function is exactly the same.
This Back to the Future model — an obvious piece of merchandise to promote the movie of the same name (or perhaps Back to the Future 2, since its design would fit perfectly with some of the outfits being sported in the futuristic 2015) uses the digit font for 3, 6, 9 to match the time circuits in the DeLorean, and has the BTTF logo with trademark. On the back is printed copyright to UCS and Amblin (UCS/Amblin also produced scale models of the time machine).
It’s the same module as the KFC watch, and I’ve seen others including one with the Golden Arches too, so a popular fast food promotional giveaway of its time.
Cool watch too – if you can get past the bright colours and the fact it doesn’t have a light, it keeps time well and ‘does what it says on the box’ – much like the movie, it’s a great snapshot of the 1980s!