A power isolator, whose purpose is to isolate power transmission wires, is one of the most widely used objects of this type found in power engineering. Power isolators were initially made of glass or, as is the case here, of electrical porcelain – at the time both materials were considered cheap and durable. Over time technological progress allowed new materials to be used for their production. One such material is silicone rubber – which is cheaper by about 1/5 than the traditional counterparts, as well as being lighter and more mechanically durable. The item presented here was produced by the factory of the descendants of the Wroclaw merchant Jerzy Giza (Georg von Giesche), which operated without interruption from the end of the 17th century until the mid-20th century in Upper Silesia. The enterprise operated the mining of coal and metal ores, a steelworks, and a fertilizer factory. In 1925 it opened the Giesche Fabryka Porcelany SA porcelain factory (previously Czuday), which produced electrical engineering products and porcelain tableware. After ownership transformations and a rebranding, production continues on the same location to this day.
Interesting fact: The surname of the founder of the enterprise is referenced in the name of a residential development for workers in Katowice, Giszowiec, originally inhabited by employees of Giesche’s company.

References:
T. Kostro, Na początku był cynk…, Sosnowiec 2004, a book fragment reproduced on the web page “Giszowiec. Poznaj unikatowe osiedle-ogród” at: https://www.giszowiec.info/pl/index.php?co=giesche (Accessed: 9.05.2021).
M. Krysiak, Porcelana na Górnym Śląsku 1922–1939 (analiza wyrobów ze zbiorów Muzeum Historii Katowic), „Kronika Katowic: rocznik Muzeum Historii Katowic”, vol. 2 (1984/1985), issued 1986, pp. 40-62, 1986.
Giesche SA, entry in the dictionary published on the “Polin. Wirtualny Sztetl” website, https://sztetl.org.pl/pl/slownik/giesche-sa (Accessed 9.05.2021).
Die Montanindustrie Polnisch-Oberschlesiens, Katowice 1922, book available at:
http://www.sbc.org.pl/Content/85010/ii344543.pdf (Accessed 9.05.2021).