I have some Callaway Tour 20 irons and am trying to identify the shafts on them. In particular, what flex they are.   The only marks I can see are.....   12inches from club head, it says "True Temper    Finest Quality     Made in USA"   Next to grip it says "9ZN3C Z3430"   Does anyone know if this code identifier the shaft and/or how to find out?   Thanks!