hallmarkings

by emma lyons
(england)

Hi I have an engagement ring that I want to get valued, however I am worried that wherever I may take my ring I may not get a true valuation, so I wanted to check what the markings on my ring mean.

The first is CT18 which I guess means 18 ct gold, the second reads PLAT, I presumed this means platinium but is this a normal marking? after PLAT there is also another marking, it looks like a backward shaped L with a dot. I think maybe the ring is not from this country you see.

It is a diamond engagement ring but they are the only markings on the inside, can you help me understand these markings? Thank you