Here is a close-up of a massive railway pole - all insulators are Cordeaux of various types. In general, some of the Irish cordeaux differ from the British ones by being pure white, in my opinion being imports from probably Germany and Czech Republic (Merklin). There are also the blue P&T marked ones made in Japan, both in small and big pattern. One of these P&T can be seen on the lower right crossarm on the double U-bracket. The brown terminal pattern ones are all marked GPO, being installed in the 10's and 20's.