My alto has a couple of trill keys that I've never seen anywhere else (my tech either!)
BTW; if your sax has separate high D access then it's the model before "The New Revelation" saxophones. I wrote some lines about Holton on another tread:
http://cafesaxophone.com/showthread.php?6158-Help!!-Can-you-identify-my-Silver-Alto-Saxophone
Thomas