The object is the ribbon used in a typewriter to supply the ink necessary to make an image on paper when the typist taps a lettered key. The ribbon is attached to two spools, which have to be fitted on to the typewriter, one each side. The one on the left will initially be full and that on the right empty. The ribbon has to be threaded through the wire that holds it in front of paper, which has been wrapped around a roller.
The ribbon has been impregnated with ink, which is now dry. It will last quite a long time as the keys are not constantly hitting the same place. The ribbon moves around the spools every time a key is hit. First from left to right until the left spool is empty and then right to left. If the ribbon has two colours the black part must be at the top. The black section will run out of ink much more quickly.
A ribbon is about 13mm wide and between four and ten metres long. The ribbon needs to be changed when the printed text is not dark enough.