Collections group separate IIIF manifests. Institutions have taken a couple of different approaches to creating collections.
You can open a truncted version of this manifest.
Note the use of the
navDate which the viewer can use to order the manifests by date.
Papers of Michael Collins (1890-1922) https://data.ucd.ie/api/img/collection/ivrla:10905
You can see some of the top-level collections that have been published here: