What Do These Gold Hallmarks Mean?

by Humphries
(Cumbria)

Hello, I have gold antique ring with a Ruby and lots of specs of diamonds surrounding it, set in 9k gold.

I had a look at the Hallmarks under a 10x jewelers loupe and looking for some awnsers please.

It had a "RJ" mark which I assume is the makers mark and a "375" mark which I know is 9k gold, along with a few other symbols eg the gold crown and another which either looks like an emblem or a face of some sort. Furthermore, the last symbol looks like a D or a B or do you think it could be the Assay mark?

Please could you help me identify these? I am wanting to sell it but need some help to describe the marks: How can I assure them the carat of the specs of diamonds together and how do i proof it is a genuine ruby?

Many thanks

Mrs E Humphries