I saw this on Gunbroker as well. Advertised as a (-3) model but appears to have some features of a (-4) model. The rear sight appears to have been swapped for a newer version with the rounded end on the top strap, appears to have been drilled and tapped with the extra 3rd screw hole (pic showing underneath the topstrap), and had Hogue grip instead of factory Pachmeyr grip. Had several other proof stampings on bottom of barrel and I wandered what they all meant.