Smoking gun,
From what I’m finding, your Redhawk is indeed one of the first shipped with the 5.5” barrel AND one of the first with the left side hammer pin flat. I have no explanation yet for SargeMO’s 1979 blued 5.5” revolver, but I continue to search.

If we live long enough, we all have regrets. But the ones that nag at us the most are the ones in which we know we had a choice.

Doug