A LUXURIOUS SPYGLASS, English, c. late 18th century, signed “Gilbert, London.” Opening from 6-5/8″ to 19″ (17 to 48 cm) on three drawtubes, the telescope is fashioned from Sheffield silver, with a matte red enameled main tube. The two lenses of the achromatic objective are notched and keyed in to maintain their best rotational alignment as determined by the maker, and the erecting eyepiece system has four elements, giving fine images. The telescope is in excellent condition, complete with its original red Morocco leather bound wood case in fair condition.
The Gilberts were a virtual dynasty of mathematical and optical instrument makers, active individually and in various partnerships from the early 18th century to the mid-19th (see Clifton). The present spyglass is a very fine example of a type popular in the last decade of the 18th century, constructed especially by the Gilberts (and see Tesseract Catalogue 85 Item 2 for more details).
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David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at firstname.lastname@example.org.