+1, that's basically how I see it as well. But there is probably a gray area as well, where a builder has gone out of business but sold their name to someone who sold it to someone else, who sold it.... For example, the Norman factory in Ashford, Kent, was started by two brothers named Norman; they sold out to TI in the 50's. TI subsequently bought Raleigh, and after 1961 the bikes labeled Norman were made by Raleigh. That ended in the early 70's. By now, even the Raleigh name has changed hands more than once. But what of the Norman name? I have no doubt someone owns it. I can only speculate who that would be, though.
Not that I'm planning to repaint my Normans, of course.
Of course, that is always possible, the company has gone out of business, and someone else owns the name and logos and stuff, in many cases Google is your friend, a quick search on Norman Cycles shows that it is owned by Raleigh which is a going concern, so contact Raleigh.