80 years young! “To me, old age is always fifteen years older than I am.” ~Bernard Baruch
80 is the atomic number for mercury (aka: quicksilver). The most common and well known use for mercury is in thermometers. So obviously thermometers (outdoor, pediatric, meat, etc) are perfect gifts but also consider gifts that are associated with specific temperatures (eg: iced tea, hot chocolate, a fan for hot days).
Traditional 80th anniversary gifts include oak and rubies. These could be incorporated into your theme.