Cut glass rummer? Any idea of age please?

I picked up this glass the other day and would very much like to know more about it.
It's very finely cut and going by the shape think it's a rummer, it has no markings of any sort and is in perfect condition.
The square base (with its chamfered edges) seemed to me to be a bit unusual and the colour itself looks like modern crystal ie no grey hue at all, the total lack of scratches to its base leads me to think it's not old too......
Can anyone suggest who might have made it or whether it is old?
Thanks!

It's difficult telling age from images but your description seems to suggest that it is 20th century and, as this type of thing is so very out of fashion, I would suspect that it's 1960s to 1980s.

Thanks.
If it is modern then I'm surprised that there is no makers mark, it is really good quality IMHO and the square base is certainly unusual.

If it was old then there would be no maker's mark and drinking glasses in general rarely have any mark.