@Dan Carmellwas nice enough to send me a sample bottle of vintage Sheaffer Kings Gold ink. The sample bottle is tiny, it holds only 12ml of ink and I'm guessing it to be from the 1980's judging from the bottles' shape. I'd never seen one before and can only guess that stores gave them out as samples or perhaps with the purchase of a pen. Maybe given out at pen shows, but were there pen shows in the 80's?
In hand the color is, perhaps, a bit lighter. Not a yellow and not really a orange either, so gold was an apt name.