I once saw a frame that was stamped 28-2. The barrel was stamped .44 Magnum and the cylinder was chambered in .44 Magnum as well.
I think that 58 is just a mis-marked frame.
In the late 1960 and 1970 era it was common practice in my part of the world to convert Model 28s to .44 Magnum by changing the barrel and cylinder. I had several done.