The power isolator is an object used in power engineering for supporting and insulating electrical conductors, in this case power transmission lines. Traditionally, products of this kind are made of glass or electrical engineering porcelain, but now silicone rubber isolators are used more and more frequently as they are about 20% cheaper than their classic counterparts, weigh less, and are more resistant to mechanical damage. The item presented here was produced by the most famous Polish utility and decorative glass factory in the inter-war period – Huty Szklane Juliusza Stolle Niemen SA. The glassworks were established by Wilhelm Krajewski and Juliusz Stolle in 1891, near Novogrudok (Nowogródek). They exist to this day but are now in the territory of Belarus. The factory supplied around 3% of the glass products on the domestic market and was present on many foreign markets, e.g., in Canada, Argentina, and Syria. The company’s catalogue included almost 2000 designs, including in the art déco style, and it also carried out individual commissions for bespoke glass products. In 1912 and 1922 the company received some large orders for deliveries of glass isolators from the Ministry of the Postal and Telegraph Service. During World War II, the Niemen glassworks were nationalised and went under Soviet administration. The isolator presented here is a model produced until the early 1930s, with a very characteristic shape with a slanted top part. The isolators were produced in three sizes – 8 cm, 10 cm, and 14 cm – and in different colours of glass.
Interesting fact: The Niemen glassworks’ products included the urn for the heart of Marshall Pilsudski, which was made in 1935. The factory also provided tableware for the residence of the President of Poland.

References:
Huta Szkła J. Stolle „Niemen”, “Polskie Zielone Szkło” blog 6.01.2018, https://polskiezieloneszklo.pl/huta-szkla-j-stolle-niemen/ (Accessed: 9.05.2021).