This no-tie insulator originates from the late 1860's to early 1870's, but were made probably up to the 1890's. Used on the railroads for telegraph and designed to hold a larger conductor for long distance. Possibly manufactured by Swedish maker Rörstrand and measures 3 1/2" X 5 3/8" (89mm X 137mm). Thank you Fredrik Höjefält for your help researching this insulator.