Hi Alan,
Ah yes... that's a screw-down grease cup. You fill the cup-shaped lid with grease, refit it, and as you screw it down grease is forced into the tube. Inside there is usually a spring steel clicker that engages in a series of detents, to calibrate the screwing down process and to stop the lid from unscrewing.
I've also seen OB-style grease nipples (Tecalemit, I think) fitted at the top so you can use a grease gun - very modern, except you need a special slide-on fitting for your grease gun.
Cheers
Leon