ah Pan Americans..... i heard a rumor somewhere that the serial numbers on pan ams was more or less random. cant validate that, but its entirely possible. by extra key, he means either: (most likely has both, but if the band director isnt a sax player he probably wont know this) 1) trill G# key. played by pressing down a pearl in between the F and E pearls when the G# key on the lefthand spatula was pressed down 2) Trill... um... E? (dont quite remember the exact note, could be an Eb. doesnt really matter, because the spring has been reversed on most saxes with this feature, making the key irrelevent) its played by lifting the F# key while the F and D keys are down. I think. its a tiny little thing on the back side of the body of the sax, across from the low B. this sax has both (in fact, its my old pan-am) www.pmwoodwind.com/instruments.cfm?c=1&instrumentid=2037&morepics=1