The barrel rib appears to be striated and the front sight looks like it is retained by a screw. The rib also appears to be too wide for a Model 28. If these are correct that is not an original Model 28 barrel. The rib should be narrow, about the same width as the rear sight base tang, and it should be smooth.
The front sight should be integral to the barrel, not added on. The barrel contour is too heavy for a Model 28, and should be distinctly tapered, not cylindrical. What caliber is the gun? Has it possibly been converted to .41 0r ,44 Magnum by changing the barrel and cylinder? It could be an original Model 28 frame that has been converted.