A diamond half-hoop ring

A diamond half-hoop ring, pave-set with circular-cut diamonds in yellow gold border on plain yellow gold band, maker's mark CSW, marked 18ct and with import marks for 1993, size P 1/2, a diamond half hoop ring, set with circular-cut diamonds in platinum within fluted yellow gold border, maker's mark ZJ and rubbed import marks for 1990, size Q, and a yellow gold spiral ring set with a line of circular-cut diamonds, maker's mark LL and hallmarked for 2005, size M