There also can be a variety of flavours for these old Octal tubes and a good example is the 6L6. I have them with the metal can, shoulder top envelope and also the straight sided smaller glass envelope as shown in the above posted link. Also 6L6, 6L6G, 6L6GT. The pins also vary from manufacturer and perhaps as mention no internal connection on a possible dummy pin or who knows perhaps if they have bases on hand for other model of tubes with a full set of pins would probably be used. If you want an adventure get into the European “valves” aka tubes which I now have and I believe they are referred to CT-8 bases with the bottom electrodes pointing out sideways or radial instead of axial prongs and I also have these in “eye” tubes as well.