I've been squinting and turning it round, improving the pics, looking at it from the inside to try to see through the iridescence, I can just about see what you mean on the pics, but can I see it on the vase? Don't be daft...
I'll try again in daylight tomorrow with a strong loup and see what I can see then...
In the meantime, if it DID say KS 1972, would that tell us anything?