14K - Not a historic british hallmark by: Yvonne Hammouda-Eyre
Hi and thank you for your question, RMB could be engraved initials, if not your grandmother, perhaps someone dear to her.
It's very hard to determine without the benefit of a photograph. Or, it could be a sponsors/manufacturers mark. How long is a piece of string? That is how many makers marks there are, and that is in the UK alone.
Your ring is definitely not British made, that I can tell you, British purity marks for 14 carat prior to 1975 was marked 14.585, so by deduction its not a british hallmark.
14ktp may indicate gold plated. You can take the ring down to your local jewelry or if you handle jewelry on a regualr basis test yourself with the Mizar (which I use), gold testing equipment on the market today, can often distinguish between gold flash, plate and solid gold as well as platinum.
