Hi Derek,
I reckon that your example is almost certainly one of the rare "green" spiral versions with an overly dense green inclusion. I have a couple of "green" grounds that are virtually black except in the very brightest light.
Chris's example does seem to be a one off. The streaky range of glass items didn't appear at Whitefriars until after this doorstop ceased production. It may well be a "crossover" item where the colours or techniques of an incoming range end up on an older design as either they were deliberately experimenting, or someone just fancied trying it out in their lunchbreak.
Quite jealous of you both.
Cheers,
Tony