Hi Pat thanks for writing in. I had a quick look and couldn't find British Maker's marks that matched your description. However the marks "9 ct" and "plat" are standard marks. The ring is comprised of 9 carat gold and platinum.
The ring is most likely of European or British origin as it is marked "ct" - in the US the "K" for caratage is the common designation.
Both metals, 9 carat gold and Platinum are very hard-wearing so it's a great heirloom piece. Demand for Platinum is increasing too. Platinum is a hard dense metal and was little used until the late 1800s. By 1900 it was very popular and continued to be right through-out the 1930s.
If you can manage to get a photo of the other marks, I would be happy to have another look.
best wishes, Yvonne Hammouda-Eyre Stay up to date with all the latest Antique, Premier and Pearl Jewelry News, and subscribe to my newsletter....