For a long time, all MJE-350s used by Bottlehead had a metal side and a non-metal side. Several manuals were written with these parts, and therefore use that description. Occasionally we will get a batch that does not have a metal side. If your MJE-350s do not have a metal side, the side without writing should be considered the metal side. This is easy to remember since the metal side is there for attaching to a heatsink. In that case, you would still want to be able to read the part name, so the writing can't be on the metal side.
