Are you talking about the lighted power switch? Or are you talking about the LED panel lamps? Or are you talking about the vacuum tubes which light up? I think you are calling the vacuum tubes "lamps," and that makes it sort of confusing? If you need to identify which vacuum tubes belong in which version: A. You check the value of the screen grid resistors for the output tubes. B. You check the bias adjustment circuit resistors. C. You check the bias split resistors. After you know which resistors are installed: then you will know which output tube belongs in the amplifier.