Help with markings

Is anyone able to tell me what the markings on this gold ring mean?

 

Is the mounting on the ring platinum by any chance?

 

Not sure I have included a picture of the actual ring

 

I am only an amateur at this but, the initials B.Bs would indicate the sponsor (sometimes called the makers mark but it didn't have to be the maker just the person or company responsible for the purity of the metal.)
18ct would signify that it is 18 carat gold and it would also indicate that it is from the UK (Gold in the US is stamped with a K not usually CT.) The PT it for platinum, which was used for the stone mount.
However, there are far more experienced experts on this site, so they maybe able to give you more information.

 

Beautiful ring Laws. Are you in Australia or New Zealand by any chance? The 18ct mark is used Down Under, though probably not exclusively there.

 

Thanks, that makes sense. And Cyprus has excellent goldsmiths.

 

The ring was inherited by my husband from his grandmother. She was married in 1942, but believe she was engaged before this several times, but could also have been passed down from her mother. Would be great to know an approximate date.

 

I think it's British, given how much presence we had there. The style is very 1920s/30s too. Diamonds in a platinum setting in 18 carat gold. It's fairly common to find earlier 20th C rings without full hallmarks.

Might be Barker Bros. I'd think most likely a Birmingham maker anyhow.