CF187

This tube was one of the last of the original design de Forest Audion E12 based tubes to be made - around 1918. It useed "dumet" wire in the press, rather than the usual platinum. (Dumet wire is a nickel iron core with a copper sheath and was invented by Colin G Fink of the G E Co Research Laboratories in 1913). Because the tubes were designed for the Navy, de Forest was allowed to use the new lead-in wire. These tubes were used by the U S Navy as replacements for a very short time in older Navy radio eqiuipment.