TR6R is a US machine as it has the "R" which means road. "C" is competition, TR6 is a "home market" machine. Yours is an early 1968 model, manufactured in '67. Trophy/Tiger engine/frame numbers started DU68364 to DU85903, build dates 9th August '67 to 26th June '68. Triumph started their production of the new model the previous year, build dates started August to the following July. Your machines' correct colour scheme is Riviera Blue and Silver, with Gold coachlines.
See if you can get a couple of good books. Authors David Gaylin ISBN 1-903706-12-2 and Harry Woolridge ISBN 1-903706-12-2 and check my '68 Trophy on my website, however mine is a home market machine TR6, lower bars, but will give you the right idea.