I have added a "most likely" ID to the thread title. What we can be sure of is that it is not from Strathearn Glass.
I am reasonably sure that this is a Caithness Glass version of the design. But a photo of the base could be very useful. All of the examples I have seen of this design from Caithness Glass, but without a "CG" cane, have had an indentation at the centre of the base (but that may not be true of all examples).
The GMB thread that Wuff linked to is useful for background information and also for the fact that it is not easy to decide on some of these weights.
Dave's weight above is the only one I have seen that was from Willie Manson's Scotia range. It shows that the central and outer canes are certainly not Paul Ysart canes, which does seem to be true of all the CG versions (and of course all of those from PY's Harland works).
I happen to now have an example which, under longwave and shortwave uv light fluoresces consistently with the lead-based glass used at CG, Wick. This is my first practical evidence of Paul Ysart making this design at Wick and therefore pre-dating the commencement of his Harland studio work and the CG versions from 1976 onward.