The piece, the size of two cupped hands and known as the Constable-Maxwell Cage-Cup, is expected to fetch up to two million pounds at the Bonhams auction on July 14."This is the most expensive piece of glass ever to be sold," glass specialist Joanna van der Lande told Reuters on Thursday.
"The most staggering thing to note about this is that it is all cut from one block of glass. The artistry and delicacy of the workmanship by someone working on the ancient Syrian coast in 300 AD would be hard to emulate today," she said.
The bowl, which would have been filled with oil and suspended from the ceiling as a light, is intact except for a small piece missing from the filigree base screen.
Most of the pieces in the 25-lot sale dating from 1,600 BC to 1,500 AD were once the property of the British Rail Pension Fund.
At the far end of the age scale is an ancient Egyptian statue carved out of a large block of black basalt and priced at up to 300,000 pounds.
At the near end is a hand-sized pre-Colombian gold statue of an alligator-headed god, priced at up to 150,000 pounds.
"These pieces ... would have been commissioned for the very wealthy in a period of stability," van der Lande said. "The ancients did like to display their wealth. They were pretty decadent."
She said she expected interest from the United States, Europe and Asia for the collection of very rare pieces -- most of which came from ancient graves -- although the weakness of the U.S. dollar against sterling could have a dampening effect.
"This is for serious collectors and museums. It is not for dilettantes," she said.