I personally reached out to Gunrunner & GGG. John didn't have a conclusive answer saying he believed REV 13 is probably REV. I3 (the letter I, not the number 1) & probably came after REV H. So I have REV. I3, REV. I3A Silver Dot, would have followed REV. H.
I thank John for pointing out 13 was in fact I3 (clearly visible once I had my glasses on). See attached.
The silver dot after the REV. I3A indicates what?
Hope to hear from George.