I’ve been trying to date my JCM 800 and the more I research it the more I get confused. The back panel serial number begins with S/A, which my research tells me it’s a 50 watter. Yet, also on the same panel it says Master Model 100w Lead and also says, model 2203. So, is it 50 or 100 watts and an 81 or 82? I defer to the experts here and thanks in advance.