The SIGNET TKN3Ea needle as found in the SIGNET TK3Ea cartridge is obsolete, however, because any "208" type needle will fit you do not have to change out your old SIGNET cartridge as it is surely still good. Cartridges rarely fail. The Audio Technica ATN-120E is the closest modern match to the Signet TKN3Ea currently available .
"212" type needles shown below also work but don't have the flip down guard.
Thin-wall cantilever Nude (natural diamond) .3 X .7 elliptical tip.
Most diamond needles are man-made glued onto a mount but this one is a single solid real diamond. This allows for more reliable performance. This fact combined with this stylus being an obsolete genuine Signet product are why our cost is significant to get this stylus. Signet was made by Audio Technica so fortunately Audio Technica found in our 208 and 212 needle families will work just fine.