The presented protractor is a device for measuring angles in relation to geographic directions when working in the field. Due to its design and function it is a device in between a steel square (which only allows plotting of 45° and 90° angles) and a classic optical theodolite (allowing any angles to be measured). Instead of a scope, the device has two vertical sights, enabling readout of the angle between the observed object and a given direction thanks to a compass in the bottom part. The instrument presented was made around 1900 in the Specjalna Fabryka Instrumentów Geodezyjnych i Rysunkowych Gustawa Gerlacha in Warsaw. The establishment operated from 1816 until World War II and it specialised in the production of surveying instruments such as theodolites, levellers, range finders, steel squares and topographic tables. The company also produced other, small accessories for land surveyors. Instruments from the G. Gerlach factory were considered to be on par in terms of quality with products of the most renowned German manufacturers, such as Zeiss. The company’s strong position was evidenced by international awards and the presence of its branch offices and sales outlets in several cities.

References:
M. Kluza, Polscy wytwórcy instrumentów naukowych w XIX wieku [in:] Polscy twórcy aparatury naukowej, ed. A. Strzałkowski, Monografie series, vol. X, Kraków 2006, pp. 277–285.
G. Gerlach najstarsza polska wytwórnia sprzętu geodezyjnego, prepared by S. Walczak, exhibition catalogue of the Museum of Technology in Warsaw in accordance with the programme prepared by the Main Commission for Museums and Exhibitions of the Polish Surveyors’ Association, Warsaw, October 1973