The BBC Reports 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.
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.
Small pictures of Mr. Bellwood included in the story.