An old germanium based bipolar transistor, with the type designation OC44, with a view to the point contact chip. There was some silicone grease removed so the chip could be seen. A little of the silicone grease are still visible. (source: https://web.archive.org/web/20230107102751/https://sites.google.com/site/transistorhistory/Home/european-semiconductor-manufacturers/philips?pli=1 Quote: "...It [Philips] developed an all glass hermetic seal using silicone grease to protect the active elements and improve heat transfer...") The rectangular plate are the base in both senses. It is the actual base of the point contact transistor - and in the second sense it the terminal base. The front of the chip has a junction and on the back the chip has a second junction, that is why it is called a bipolar junction transistor - or short BJT. Today in modern bipolar silicium based planar transistors, the base terminal is not the physical base. Modern chips do not have visible junctions, the junctions are there, but they are below the surface of the transistorchip.