this is an unusual Hallmark question. I wouldn't think it would be a maker's mark, because even in the very unlikely event the maker's name was "hallmark" he would not have wanted to use a name that would confuse the customer especially concerning gold quality, so I'm leaning more towards it being more of a guarantee of the authenticity of the gold quality. Now if you find out it is not 14 kt gold then....
there were heavy gold filled rings marked SOLID GOLD that were made in the late 1800s.
