This is a new Lucas-type SRB316 starter solenoid, but not supplied by Lucas or in a Lucas box.
It is the correct starter solenoid for most six-cylinder Jaguars, including XK120, XK140, XK150, E-type, Mark I, Mark 2, Mark VII, Mark VIII, Mark IX, Mark IX, S-type, 420, 240, 340, Daimler 2 1/2, 250, SP250, as well as early MGB, Triumph TR2, TR3, TR4, big Healey, Land Rover, and many others.
Genuine Lucas SRB316 solenoids are also available; see Related Products below.