The following models of signal boxes were seen on various layouts at the SW Herts Model Railway Society's exhibition held on Sat 11th May 2013. I have given brief details of the scale and intent of the model after each picture.
7mm/ft scale (0 gauge) - set in 1877 south of the Clyde. Unusually shows a station under construction, hence the partly finished box, complete with carpenter's bench.
Also 7mm/ft, set in the 1970s on BR Southern Region on a fictional line built to serve a developed Biggin Hill airport.
4mm/ft (00 gauge), fictional terminus in the Nottingham area built by the MR but with LNWR having running rights. Set in the 1895-1920s period. The box has not been completed and awaits the typical MR windows.
The model signals however are the Dapol LMS/BR UQ models that were put on the market last year and perhaps are not quite right for the period portrayed?
4mm/ft (00 gauge), NW of England, 1980s, fictional location representing a MPD and yard serving industry in the Runcorn/Widnes area. Close-up of the quite well detailed box.
More views of these and other layouts can be seen at http://s938.photobucket.com/user/John_S_Webb/slideshow/SW%20Herts%20Model%20Railway%20Show%2011th%20May%202013