The Marshall Mercury 2060 was a small mail-order only valve guitar amp, made at the Bletchley Marshall factory, and available in the early 1970s. At just 5 watts, and with a 12" cone, it is not powerful enough to keep up with a live band, although louder than perhaps you might think. It does, however, make a great recording amp.
Sound-wise, this Marshall has a very bright tone, and when pushed to higher volumes, has a superb overdriven sound. It is a true hybrid, with a transistor preamp, yet powered by one EL84 valve. Listen to some of the sound clips below.
Feature-wise, this amp is fairly simple: just tone and volume controls, but with a foot-switchable tremolo effect, with a further two controls: speed and intensity.