This key is an S-R Cotel straight key. It is modeled after (but slightly larger than) the WT8Amp key. It was manufactured by the late Jack Sykes, G3SRK, who became a silent key in June 1997, at the age of 95.

"Under the business name of Lingard Electronics, Jack was the manufacturer of the so-called 'S-R Cotel' key, claiming in MM1, in 1986, when still making keys at the age of 84: 'There are now 50,000 of my keys all over the world.' "

The above quote is from Morse Magnificat Nr 53, August 1997, and was provided to me by John, GM4GZQ. I am VERY grateful for the information, for I have never seen one of these prior to obtaining this one, and have seen none since.