From Wikipedia, Nov 2012:
J & L Randall Ltd was a British toy manufacturer, based in Potters Bar, which was in Middlesex until 1965 and then in Hertfordshire. The company flourished in the 1950s and 1960s and placed regular advertisements in Meccano Magazine. It was one of the main competitors to Mamod for models of stationary steam engines.
The company used two trading names:
Merit for general toys
SEL (Signalling Equipment Ltd) for technical toys, e.g. electric motors, steam engines and student microscopes. It is believed that the term "signalling equipment" originally related to items such as Morse keys and sounders.
In 1978 the company was bought by Letraset for 12.5 million pounds.  
The company no longer exists but some of the products, especially the steam engines have become collectors' items.