I'm not exactly positive, Greg - I would say '70s, perhaps even including the early part for some of the bowls/ashtrays in this sort of style. They're not scarce, but they are rather gorgeous and quite complex - there's crizzling in silver chloride in the base clear glass, and lots of interest with the colours and textures of strapping outside, giving them a chunky sculptural quality. This sort of strapping was put around the knops of the chalices during Michael Harris' time, it's certainly a technique and design he was responsible for introducing at Mdina - as was the crizzle bit.
I like these beasts. I have a few in various shapes and sizes and colourways, but I do like the bluey ones the best.