There’s little available information on this apparatus. It was discovered in Rudolph Christensen's apartment in Copenhagen, shortly after the death of Christensen’s daughters in 1963.
We do know that Christensen’s business partner Hansen was a acquaintance of Hans Børging (1879 - 1955), a little known cabinet maker and amateur inventor. We also know Hansen had commissioned several furniture pieces from Børging for his apartment in the early 1920’s.
It is thought that this device was one of a small number of inventions that Børging developed occasionally throughout his life. So far no further information on the device has been uncovered, and no patent applications or similar to describe it. It is believed to have been made during the late 1920s or early 1930s, the body seems to be made from a rare (Cuban?) mahogany, and interestingly, there are other materials used that were still in development at the time (early types of plastic and aluminium).
It is apparent that it is hand held and would most likely be powered by an external (battery?) power source, it appears to have two elements that are thought might be for sensing moisture, but for what function remains a mystery.