Editing Red telephone box (section)

=== Manufacture ===
The K1 and the later K3 concrete kiosks were produced at various (and largely unrecorded) locations, around the country. This made quality control and supervision of the manufacturing process difficult, when compared to the GPO's experience with cast-iron [[post box]]es, and was an important aspect of the GPO's move towards cast-iron telephone kiosks. Over the years, five foundries were involved in this work for the Post Office. Lion Foundry in [[Kirkintilloch]], MacFarlane (Saracen Foundry), and [[Carron Company|Carron Ironworks]] near Falkirk all produced batches of the K2, the K6 and the K8.  Carron produced the single batch of K4 kiosks. The other two manufacturers were McDowall Steven and Bratt Colbran, both of which produced only relatively small batches of the pre-war Mk1 K6.

Many kiosks have been fitted with replacement backs; unmodified examples usually have the identity of their manufacturer marked on a plate on the outside at the bottom of their back panel. The only exceptions are the few Mk1 models made by Bratt Colbran, which are anonymous. A supplementary way of identifying the manufacturer is by means of casting marks on the various component parts – i.e. LF, CC, MF, MS and BC – which were used to various extents over the years. A more consistent manufacturer mark can be found at about shoulder height on the inner face of the back panel. These marks generally identify both the manufacturer and the precise model of kiosk. Up to around 1949, the year of manufacture is also included. The non-BT K6 kiosks erected later, usually painted black, are for the most part new castings from new manufacturers.