Fender Silverface amplifiers were built between 1967 and 1981. They are often referred to as Silverface (or Chromeface) because of their brushed aluminum face plate. The first Silverface amps, manufactured between 1967 and 1969, had an aluminum frame (trim) around the grillcloth, mid-1960s "tailed" amp logo and the AB763 blackface circuit. An even rarer feature were the vertical, narrow black lines, which separated knob groups in the control panel. This cosmetic detail (later referred to as "blackline") was abandoned pretty quickly, though. All of the Silverface amps generally had blue labels on the face plate, but in some rare exceptions (such as the Bronco) the colour was red instead. Some transitional models produced before the "tailless" period in 1973 featured the AC568 circuit, still retaining the tailed Fender amp decal introduced in 1964. In 1973 CBS changed the "tailed" Fender amp logo to the modern-looking "tailless" style (which was first introduced in 1967 on the student Bronco amp). A master volume knob and a pull-out "boost" pot were added on some amplifiers, followed by ultralinear output transformers and a "scripted tailless" amp decal (featuring a "Made in USA" script in the bottom) in 1977; the power was increased between 70 and 135 watts on certain models. All Silverface models usually came with a sparkling silver/blue grillcloth (some later models had a non-standard sparkling silver/orange grillcloth, and a black grillcloth was even fitted to some production runs). The Silverface control face plate was discontinued in 1981 and the second series of the blackface amps designed by Paul Rivera were produced. Paul Rivera went on to found Rivera Amplifiers. Fender made a limited-edition Mini-Twin practice amplifier modeled after the mid-70s Twin Reverb models in 1996. The Silverface Edition MT-10 had the authentic look right down to the grillcloth. This 1-watt Twin featured 3 in. speakers, "skirted" style Fender knobs for Gain, Volume, Tone and Power and included a tilt-back stand.