Sort of familiar with having built it signalling wise it comprises of a starter ,home and indicator for the catch point,nicely illustrated on a set of photos avaliable from the Bluebell Railway.If you go onto their website,,then go to the museum section you will see a bit for Photograph collections ,the one you want is the John Smith collection,there is a large Irish section done by dates,try November 1959 Photo ref 7-98-7vis especially good in that respect.The great thing about these lists is the prints are displayed so you can see what you are getting.Hope that helps Andy.