The 20th Anniversary amps should have the letters "AS" in the serial number. And - obviously - they should be made in 1982.
Btw, I have the same amp as you, same colour, build in 1983 and it is great. I would never sell it, lol. Circuit is a little weird though, I would love a refined reissue of that amp. I mean, come on, it's the Schenker amp! Also, at least later models, it's the sound of Rage against the machine.
Btw, I have the same amp as you, same colour, build in 1983 and it is great. I would never sell it, lol. Circuit is a little weird though, I would love a refined reissue of that amp. I mean, come on, it's the Schenker amp! Also, at least later models, it's the sound of Rage against the machine.