That's a beauty!
Very nice 4-screw .44 Magnum...and totally correct. I have her sister, s/n S177963. Mine is also 6-1/2" bbl., blued, with Coke Bottle stocks. According to Doc44, 2 of these revolvers shipped in July 1958- maybe it was yours and mine! Do you have the original presentation case and goodies with your .44 Magnum? Mine came with a much later mahogany presentation case, but I wish I had the original blue/black pebble grain box. Enjoy!