I found a Old Model .44 Blackhawk Flattop (BHK46), s/n 28588, in a gun shop in Sacramento. It's uncoverted & in pretty good shape. Let me know it you want the shop's contact info.
Didn't think to ask the shop owner if I could remove the grips to check the grip frame. The grips seemed to be dull. Maybe oiled? The grip medllions were with silver eagles. I plan to be by this shop on Sat & will look at it closer.
Well, as Flatgate says, the fact that those are likely New Model grip panels almost assuredly means the gun has an XR3-RED grip frame . . . unusual and scarce. Serial number range looks good, too.
XR3 grip frame, small founders mark "ALCOA", long throw ejector rod housing, flat ejector rod button, loading gate is turning plum, blueing loss in multiple locations (85% plus condition?), scuffs & some scratches.