HEAD MARKING SHALL BE RAISED OR DEPRESSED (. O10 MAX) AND ARRANGED AS FOLLOWS: MARK WITH BASIC
NUMBER (NAS OPTIONAL) EXCEPT MARK .1380-32 SIZE WITH '6' AND ,1640-32 SIZE WITH 'E'. MARK ALL SIZES WIT)
MFR. SYMBOL, LENGTH DASH NUMBER AND RECESS NUMBER ENCIRCLED, RECESS NUMBER TO BE APPROXIMATELY
25% LARGER THAK OTHER NUMBERS.