Evening (Morning!) All,   Just a quick question - When did the Southern begin introducing Rail-Built posts for Upper-Quadrant Signal Arms? I'm assuming, with that question, that the posts may have been brought in before the adoption of Upper-Quadrant arms (1926/8?) for new installations and renewals, though I seem to recall the rail posts were a later invention.    I ask this for a layout which is intended to be set between 1930 and 1932, for now, though later on it will prob