Home Forums General Discussion Shot Peening Process, Intensity, Coverage Meaning of A2 intensity unit

I understand what an intensity specification followed by A, C, or N means.

I have been reviewing 40-year old drawings and specifications and have been coming across callouts like:
"Intensity 0.008-0.012 A2"

What does the "2" in "A2" mean? Is it officially defined anywhere? I suspect it is obsolete, but I still need to know.

Thanks.

Jim Andrus