Card 79 is all about semi-postals. No, I am not talking about people who sort of lose it in a post office. Semi-postals (at least in the US) are stamps that cost a bit more than their face value — the difference (minus admin costs) is donated to a designated cause. Semi-postals were introduced (in the US) in 1998 and have generated over $1 billion in donations since then.
There are six semi-postal US stamps that I am aware of. They raise (or raised) money for breast cancer research, PTSD, endangered species, Alzheimer’s research, domestic violence prevention, and FEMA.