this link explains the schilke method:
http://www.schilkemusic.com/mp-8.html http://www.dallasmusic.org/schilke/M...0labeling.html
you may also want to look at the stuff the Karl Hammod wrote:
http://www.trumpetmaster.com/forums/...pic.php?t=1269
I must warn you that after you learn the Schilke method, you may question the number and labeling systems on other manufactures, most of them don't make much since espically when it comes to comparing rim contours...
hope this helps,
-marc