SA-20 writes:
11.1.4 Plates Produced from Coil and Qualified
Using Test Specimens Taken from Test Coupons Heat
Treated by Other than Stress Relieving — One tension test
coupon shall be taken from each coil.

It is not understood why this procedure may substitute the three test coupons (beginning - mid -end of the coil). And also. if the test coupon is heat treated (e.g. normalized) it is not representative of the coil not normalized. There must be something that I do not understand. Do somebody have an explanation?
Mauro

It a record, is it not? 33 visits and no answer.
I try my answer reading Note 1 in SA-516:

NOTE 1: For plates produced from coil and furnished without heat
treatment or with stress relieving only, three test results are reported for
each qualifying coil. Additional requirements regarding plate produced
from coil are described in Specification A 20/A 20M.

This gives me the direction: three specimens shall be taken.
Regards.
Mauro