I've recently relieved someone of a Trace Elliot AH500S. The Head appears to be in excellent condition, however its a bit of an oddity to me. The previous owner tells be its rated at 250W. (I thought the model was rated 500W) Anyway there are only 2 controls on the amp. volume controls, one with a hi pass and the other with a low pass output. oh yes you can control the speed of the fan (why you would want this function is beyond me?) and it has a switch called ultra violet (which makes absolutely no difference to the soundwhether its switched on or off). Anyway, it appears to work fine. Does anyone know how I can identify its age or locate its spec. using the serial no??