IMO renickel, possibly a rebarrel as well. The lettering on the left side of the barrel doesn't look right for an early 60's 28. Should have smaller stamped lettering and a lazy ampersand IIRC.
Seems like a lot of modifications to the gun, plus the stamping issue. To me it reads Frankengun, and the top I'd go would be 550 myself. and that would be after a hands-on inspection. I'd have to see under the rubber grips, they trap moisture which can result in corrosion. Also, the hammer and trigger should be case hardened. These look bead blasted, which could be an indicator of other things happening with the action.
The revolver market is softening. The only revolvers bringing top dollar are all original 90%+ finish with the box, papers, original grips, etc.