As for
Sir Isaac's reflector telescopes (he invented the reflective telescope in 1672), an original is believed to be owned by the
Royal Society of London. Newton was the President of the Royal Society from 1703-1727. The telescope was presumably presented to them in 1766. I say "believed" because no one is 100% positive that the telescope presented to them is really Newton's handiwork.
Here's a link to the first page of a research paper on the topic...unfortunately you have to subscribe to the publication to see it in it's entirety.