The glass body, of pale blue-green colour, pinched or moulded with twenty-two ribs.
Glasses of this type were made throughout the Roman Empire during the first century AD. Some have been excavated in Northern Europe. A very similar example is set into a panel of the Ambon or Pulpit of Henry II in the Palatine Chapel in Aachen.
The Ambon was built by Henry II, the Holy Roman Emperor between 1002 and 1014 and is considered one of the most significant works of the Ottonian period. Set into the beaten gold panels are ivory reliefs and exceptional treasures of antiquity in rich profusion, including agate and rock crystal vessels. The pulpit has undergone numerous restorations in the 19th and 20th century and the Roman glass bowl is thought to be a later addition but very much in keeping with it.
For an explanation of how such bowls were made, see: https://www.theglassmakers.co.uk/archiveromanglassmakers/poster03.htm
Typical weathering. Two short stress cracks.