Found this tie tack in my dad’s jewelry box and would like some help in identifying the hallmark. Stamped “SILVER” on one side of the post and the hallmark on the other side. Tried my best to get a good picture and hope that someone can identify it. The stone that is mounted on the tie tack appears to be an opal, but it is very cloudy/milky and not any color or fire. Thanks for your help, John.
