It's always great to see a fillet brazed ATB. It's also interesting in that it only has a double crankset paired with a medium range rear derailleur. It's obviously a frankenbike or somebody had a very unique perspective on custom builds. I find it hard to believe that someone would have used a tubular steel seat post on a frame of that level!
The SunTour XC Rollercam dates 1985-1986. The rear derailleur is 1986-1987 but the SIS ATB levers did not come out until 1987, so we already have a conflict. Short of contacting Litton, the best method of dating it will probably be to remove the fork, as it appears to have an off-the-shelf Tange unicrown fork, which should have a date code on the steerer tube. That will provide a "no older than" date and the frame was probably built within a year of the fork.
On another topic, I trust the pictured newborn is not yours, otherwise you will be in deep trouble for having more flicker pictures of your new bicycle than your child. If it is yours, congratulations, and rectify the picture situation immediately or n+1 is in jeopardy.
Last edited by T-Mar; 01-16-17 at 08:37 AM.