Left: clear plastic jar filled with black rods (wires) with glass beads on them through which the distinctive reddish color of oxidized copper is visible. Right: another jar, filled with coppery-colored rods (wires) with glass beads on them, the color in the beads matches the ones on the left.
Decades ago, I saw a surplus store selling these, marked as "silicon monodes". Years later, I found the jar on the left, but they had turned black? I was rather disappointed, as I figured I'd never see more. But apparently past me was a "buy two of them" sort, as I found a second, intact jar.