Where were the bakelite modules made? Did BR produce or assemble them in-house at one of its S&T workshops, or did they buy them in ready-made from a supplier?
For the bakelite illuminated block-shelf indicators, there seem to have been two types. One with a large coloured glass dome, that was interchangeable with those on K and L frames, so I assume was made by Westinghouse. The stencil version had a flush face to the box. Then there was the type that had the indication in a tube protruding from the front of the bakelite box. Were these from a different supplier? The bakelite boxes all seem to have been about the same size, so was there a BR spec for these?