The National Library of Wales has been criticised for the way it dealt with thefts valued at £100,000 from its collection.
The library lost maps worth up to £100,000
Razors were used to steal a number of maps dating from the early and mid 17th century from the library's Aberystwyth building.
But a four-month delay in informing dealers of what had been taken may have prevented the maps being recovered, according to the Antiquarian Booksellers Associations.
But the library said it had been advised by police to keep the thefts quiet.
The thefts, which were discovered in 2001, were believed to have been linked to similar losses in Finland and Denmark.
Detectives made extensive enquiries, but none of the maps have been recovered.
Speaking to the Observer magazine, the ABA president Jonathan Potter said dealers were more likely to notice maps for sale on the market than police.
Police want to question Peter Bellwood about map theft
"The problem was that by the time we knew what was missing it is was too late," he said.
"Most of the maps had probably already been sold on."
Detectives at Aberystwyth are trying to trace a man wanted for questioning in connection with the thefts in Wales and abroad.
Peter Joseph Bellwood, 50, is listed on the Metropolitan Police's website as one of the 10 most wanted fugitives in the UK.
Staff at Aberystwyth were alerted to the thefts after reading that Mr Bellwood was suspected of raiding European library treasures.
They checked their records and realised he had visited the National Library, and subsequently uncovered the rare maps were missing.
The items can be sold for between £500 and £10,000 individually to specialist markets.
No one at the library was available for further comment.