Royal Scot Whisky is a blended Scotch whisky rather than a single malt. From the description you've given, this will have been a bottling for the London, Midland And Scottish Railways who ran a chain of hotels prior to the formation of British Rail. The motto "Heich abune the heich" means "High above the high" and has an association with The Gleneagles Hotel. This was one of the prestigious hotels run by LMS in its heyday. However, Royal Scot Whisky was bottled later as well - see this example bottled for British Transport Hotels on The Whisky Exchange website http://www.thewhiskyexchange.com/P-14384.aspx
Most old blends will sell at auction for smaller sums than single malts. Without a photo, it is difficult to verify the age of the bottle. It's value will depend on the condition of the closure, the label and any packaging, but it looks like a blend done for a hotel group and does not appear to be one of the major blended whiskies that attract larger sums from collectors.
Depending on where you are based, I can put you in touch with an auction house if that would be helpful.