Well, eleven known now (but still a rare gun!):
550-00502, 550-00547, 550-00638, 550-00659, 550-00660, 550-00667 and 550-00722, all apparently the KSRH-9 9-1/2" model.
and then there's also the known "U" marked "used" guns, also all KSRH-9:
550-00513U, 550-00524U, 550-00577U and 550-00640U
I do have one sn though that throws a wrench in the whole scheme of things. 550-00607 is marked "SUPER REDHAWK" on only one side.
And I'd sure like to hear from anybody with a gun somewhere between 550-0722 and 550-01000 or so with "SUPER REDHAWK" on only one side.
Would give us a better idea how many double rollmarked guns are really out there. Right now it only stands at maybe 225 (since Ruger started serial number production at 550-00500 and picked up with the earlier serial numbers at a later date).