This pattern of signal arm was introduced by the GWR in 1887, and was used for new installations and renewals until the advent of steel arms (S0015) in 1930. Note that the 5′ arms are for use on posts greater than 26′ tall.
The actual size of the fret is 85 x 53mm; it is etched in 0.012″ brass.
To model a complete signal as shown below, you will need: a wooden post (S006 or S0028); a finial (SC005); a lamp (SC004); a balance weight (SC0041/1); a ladder (S009 series); and a platform (S008/5). A very few signals had a lattice post (S002, S0023).