Three men were each sentenced to 47 months in prison on Friday for the theft of an ornate Romanian gold helmet and bracelets in a raid on a Dutch museum. The Northern Netherlands District Court said the three men, whose identities were not released in line with privacy rules, warranted a custodial sentence "because of the nature and gravity" of their crime.   The robbers used explosives to force open a door during the overnight heist in January last year, the Drents Museum previously said .