I’ve been digging through the storage cupboards of the Astronomical Society of Edinburgh and we have this 3 inch refractor, donated to us in 1942 by Lord Morison. No maker’s mark on it at all. I’ve searched to find what it is but with no success. It’s similar to many but not identical to any.
I’ve had a look on line and looked through a few books both for the telescope and for the event (Lord Morison handing over the telescope) and I can’t find anything. As you say, several of similar design, but none VERY close. The altitude bar, the fixings to the mount, the location of the focus knobs, the combination of exposed and covered brass…
It would probably be worth contacting the antique Telescope Society. Also try the Society for the History of Astronomy as they will likely put a picture of it in a coming publication to broaden exposure.
James [Librarian for the Society for the History of Astronomy]