Inherited Antique Ring

by Trinity
(California)

I recently inherited a small gold ring with a diamond and two sapphires from my Grandmother. I don't know much about it other than it was purchased from an antique shop in London about 12 years ago. It is stamped with what looks like PLAT 1801 on the inside of the band. I am just curious if I can find out the age and origin of the piece. I tried to take a picture of the stamps but they are so small that nothing came out. I have uploaded a picture, albeit blurry of the ring in hopes that the style will help. Thanks for any information about this beloved ring.