Collingwood of Conduit Street

The ring has the following hallmarks:

18k JN on one shank
750 (in a rectangle), what appears to be a dot or circle (inside a square), a kind of crown shape (inside a square) and the letter h (lower case, inside a square).

it is a pretty white gold or silver sapphire ring surrounded by tiny diamonds around the sapphire and down the shanks.

it is in an old pink leather box saying 'collingwood of conduit street' on the inside. Thanks for any help!


am very puzzled as to the date and possible value of the ring. any ideas?

thanks so much