These days the clasp or closure for contemporary copes are usually tabs of stiffened cloth which feature a hook and eyelet arrangement, but in years gone by, the metal, sometimes jewelled ornaments of closure sewed to each side of a cope were pretty impressive and featured chains which connected the two side motifs. In existing vestments from the 20th century, inexpensive round or hexagonal disks are sewn on each side, and closed by means of a plated chain. The disks often have IHS, a heraldic design, cross, or other religious symbol pressed into the metal. Humeral veils will also be found using the morse and chain closure, although more commonly ribbons seem to be the case. The now-rarely-seen cappa nigra or cemetery cloak used to sport a pewter or silver morse and chain and looked so graceful blowing in the wind in winter. The big mystery for me is just where the word “Morse” came from originally. The Pope is wearing a morse of unusual size in the photo above.
“Also called the Monille, Firmula, Firmule or Pectorale, the name originally referred to the rectangular ornamented piece of material attached to the two front edges of the cope near the breast to prevent the vestment from slipping from the shoulders. Morses were provided with hook and eye, and were often richly ornamented with embroidery or precious stones. Later, the name was also applied to metal clasps used in place of the of woven fabric. The clasps, however, gradually lost their practical use and became mere ornaments, which were sometimes sewn firmly to the flaps that served to fasten the cope. This was the case when the clasp was very heavy or very valuable. As early as the thirteenth century we have evidence that the clasps formed distinct ornaments in themselves. Many churches had a large number of such morses usually made of silver covered with gold, they were ornamented with pearls, precious stones, enamel, architectural designs, small, figures of saints, etc. They were generally either round, square, quatrefoil, or like a rosette in form. There were also more elaborate and at times peculiar shapes. A great deal of proof of the desirability of costly morses is shown by the old inventories and by the numerous medieval morses preserved (especially in Germany) in churches and museums.” (Catholic Encyclopedia)
Below a photo of the Queen with two of the blue copes of Westminster Abbey showing a cloth tab morse (the copes also appear a tad short on the clergy).