I remember the US Viking landers that made their way to Mars in 1975. But I knew nothing of the Russian Venera program to explore Venus between 1961 and 1985. I learned about this program recently and was amazed to learn that they had successfully returned images from the planet's surface. The Venera probes are, to this day, the only craft to have visited the surface of Venus and the images they returned are the only images we have of the planet's surface.
Running across the lower half of the stamp you can see the surface image taken by Venera 9. This was the first image of the Venetian surface ever taken. The surface of Venus experiences temperatures of 465C and an atmospheric pressure of 90 bar. That's equivalent to the heat inside a hot oven at an ocean depth of 900 meters. It rains sulfuric acid on Venus but the rains never reach the surface because the extreme heat evaporates the rain as it falls through the sky. These probes were able to relay information to their orbiting satellite counterparts for about an hour before radio contact was lost.
Images returned by Venera 13 and 14 are somewhat more impressive but they are still just a mere glimpse of the Venetian surface. The later probes returned colour images.