Today, I took apart, cleaned up and reassembles an old SunTour Superbe 5300 derailleur (c. 1984), and I noticed something quite odd...to me anyway. It doesn't have a barrel adjuster, and a standard (modern) ferrule doesn't fit...Is there a piece that I am missing?

I am working on a 1985 Team Fuji and so far, I pretty much spent a good part of the afternoon cleaning, polishing, greasing up parts to get them in working order, but went to cable it up to check operation and came across this little hindrance. This is my first classic/vintage restore, not a perfect one, but will make a good daily ride...