Decoding Your Gold Ring Hallmark: Understanding 585 & the 'D' Mark

Question
I have been given a yellow gold coloured ring, solitaire diamond about .25 carat. inside the ring is stamped 585 and has a capital D mark with what looks like a drawing pin/tack going into the top of the D

Answer
Hi Lynne,
Thank you for writing.
As you may know the 585 means 14K gold. Im sorry I'm not familliar with that "D" Hallmark.
I wish I could be more helpfull.
There are so many of these hallmarks it's impossibal recognize them all.
Sincerely,
Arthur DeMello GG (GIA)