Origins of My Engagement Ring?

by Ali
(Nottingham)

The only thing I know, is the ring was purchased approx 25/30 years ago from an antique jewellers in Oxford.

I believe it to be 18k gold with a diamond and have been told it is not English!

Visible marks are: 14K, 18K, F (in a diamond shape), J (in a diamond shape), image of a crown (in a oval shape)

Please see the images provided.

Any information you may have would be gratefully received.