Contact goniometer with detachable arms

Newman, London
Contact goniometer (brass and steel, semicircle diameter 7.9 cm) with detachable arms in dark plush-lined leather-covered case (10.9 cm wide).
Signed "Newman, 122 Regent Street", 1st half 19th century; this must be John Newman who had his business at 122 Regent Street between 1827 and 1862.

private collection