I've had this WW2 Germangrounding stake for some time which came to me in "very relic" condition and I have only just got round to de-rusting it, 2 weeks of electrolysis followed by chemical rust treatment. I had assumed that it was just a grounding stake for use with radio/communications equipment but looking online just now it appears to be much more interesting. Apparently, according to what I've read online and subject to it's accuracy, these were sometimes used by the Germans, during WW2, with their field telephones with the idea being that you only needed one wire between the 2 phones with the 2nd connection going to the earth stake, clever ehh. Obviously useful if you were short of wire. Apparently the hole in the top of the stake is so that water could be poured through to improve "connectivity" to the ground. Apparently the only downside was that it was possible to listen in on the conversation through the ground but don't ask me how that was done.