UNUSUAL PARALLEL-MOTION DRAFTING COMPASS, c. 1900. Made of brightly plated brass the compass stands 6-1/2” (17 cm) tall when closed. Each arm is doubled, opening on different centers, the linkage causing the lower legs to remain parallel as the arms are spread apart. Thus the center point, and the pencil or ink pen, always remain vertical, even when drawing large arcs or circles. Accessories include a 4-1/2” long extension arm, interchangeable pen and pencil, adjustable reversible center pin on spring-loaded mount, and container for pencil leads. An unusual instrument, in excellent condition throughout, complete with fitted case. $450.
Ask the Dealer
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.