The British Museum has revealed the types of items believed to have been stolen from its collection.
The museum in London said the vast majority of items were from the gems and jewellery collection, and are mostly from Greece and Rome.
Images provided by the institution are only similar to those that are missing, and are still in the collection.
• Classic Greek and Roman gems
• Gold rings
Some of the jewellery is believed to date back to the Late Bronze Age (1500 to 1200 BC) and the Hellenistic and Roman periods.
Gems, cameos or intaglios were described by the museum as small objects often set in rings or left unmounted.
They can be made of semi-precious stone or glass and can feature mythological scenes, animals or objects which could have been hand carved into them, or produced from a mould.
Back in August, the museum said items from its collection were "missing, stolen or damaged" and a staff member had been sacked.
It is believed the items were taken before this year began, and over a "significant" period of time.
An estimated 2,000 artefacts had been taken, according to museum chairman and former chancellor George Osborne.
"Someone with knowledge of what's not registered has a big advantage in removing some of those items," he said at the time.
The institution has now said "60 items have been returned, with a further 300 identified and due to be returned imminently".
In the fallout of the items going missing, museum director Hartwig Fischer resigned from his position along with his deputy, Jonathan Williams.
Individuals who believe they may be, or have been in possession of the missing items, have been encouraged to get in touch with the museum.
The museum said it has enlisted the help of specialists, including leaders in the study of gems and jewellery, to offer assistance in retrieving and identifying the lost items.
A Metropolitan Police investigation is also under way, and a man was questioned about the incident on 23 August.