I'm pretty sure I know what it is, although I don't know the actual English name for it, as English nautical terms is not my forte. In Swedish it's called a "logg" and the English word could well be something similar, since we have imported many English nautical terms into Swedish. Anyhow, the device is (or was) used to measure distance travelled in the day of the sailing ships. The device was tied to a rope and dropped over the side for a pre-determined length of time. Distance was then read off using the dials on the side of the thing. Using time and distance travelled the speed of the ship could the be calculated.

If I'm not mistaken, those purple potatoes are not in fact the result of any radiation experiment or space travel. They are called Blue Kongo (Blå Kongo) and are sold in many grocery stores where I live (Sweden). They have been grown in this country since sometime in the thirties. They make a very interesting mash, or a cool potato sallad with some yellow or white ones.