I wondered if it's actually a digtal watch chip (2.5V could have been a couple
of mercury cells in series, LED watches were not uncommon back then).
In which case it would not normally have come in a 0.6" wide DIP. Perhaps
normally it was a bare chip directly mounted on the watch circuit board or
something.
The DIP version would be unusual, which is perhaps why we can't find data
on it.
-tony
I think you are on to something. That would make perfect sense.
Marc