Dunhill is a UK-based maker of upper-end products such as menswear, timepieces, leather goods, pens and cufflinks, many of which have appeared in James Bond stories and movies. The Rollagas lighter, introduced in 1956, was Dunhill's first butane lighter; it employed Dunhill's thumb-roller design, which replaced the traditional flint wheel. Each Rollagas comes with a serial number that includes the date of manufacture. However, because the Dunhill company doesn't make its serial-number-deciphering method public, if you want to date your Rollagas, you'll have to contact customer service.
Look for a serial number on the bottom of your Rollagas lighter. If the number is there, the lighter was made in the 1970s or later. Older models have a serial number inside the lighter; a Dunhill technician must take apart the lighter to access the number.
Take a picture of the lighter and of the lighter's serial number with the digital camera.
Contact Dunhill customer service via email (firstname.lastname@example.org), attaching the digital photographs of your lighter and its serial number. A representative will investigate the manufacture date of your lighter and get back to you.
Ask customer service for an address to which you can send your lighter for examination if it's one of the older models with an internal serial number.
Don't try to take apart a Rollagas lighter yourself. It has a finely made mechanism and can easily be damaged by untrained hands.