I can open mine up if necessary... it means I'd hafta' un-rack it... if the OP has easier access to theirs that'd be better. On the other hand, I always wondered if my serial number was inside or under the sheet metal...? It isn't stamped or printed where it says serial number, just blank. It is a Santa Rosa-made unit. (doesn't matter, I just gig with it) It does advise 117v on the back panel.