Star Sapphire Ring from Thailand - bought in 1967 (stamped 18K?)

My Mom had tagged items that meant something specifically to her off and on. Some she put in the safe deposit box albeit it was more for sentimental reasons. Honestly though, I love this ring. I will post new pics once I clean it. I am so glad she tagged that she got it from my Dad from when he was stationed in Thule, Thailand. Do you think I'm reading the stamp correctly and it says 18K?? I take it this was meant to be a silver ring??? White gold? Unsure....