Thanks. It would seem that the main vise body carries the differences. The distance from the back of the swivel jaw piece to the base of the vertical channel is 11/16 inch in mine The channel is 1/8 inch deep. So if the channel was not original, the total spacing there would have been 13/16 inch. Yours seems less from your photos. The back portion of the top has been milled off with the result that the top of the vise body is all milled with two different layers of flat. The back vertical profile of the main vise body is vertical on yours and mine cuts back in toward the dynamic jaw side. This inward flaring surface is cast and not milled in. At the bottom, this is 0.34 inch in from a vertical line down from the back edge. In mine the cross pin hole that holds the swivel jaw locking pin in the body goes completely through the body and the pin has a "button" head on the end. The pin protrudes 0.025 inch. Yours looks to project be more and has no button head. Looking at the back side of the main body cavity, the dovetail slide sides for the nut do not project out beyond the main body in mine. However, there is evidence of metal removal in that area, as the removal did not actually clear the base level. This is consistent with someone trimming off these slides post casting. It is hard to tell, but they probably were cast like yours, as yours seem to project out. They end about 0.027 inch in from the bottom of the flared in sides. The nut retaining pin hole center is about 0.307 inch back from the flared in sides. It is easier to measure this distance from the bottom, it is 1.395 in from the back edge of the rear mounting tab tip. The sides of the main vise body constitute two parallel sections. The back portion is 1.182 inch side to side and the front is 1.385 inch. These differences are transitioned with a flat bevel that is 0.380 inch in width along the surface of the bevel. Yours has more of a rounded transition it seems. So there you have it, at some point in time, the body mold pattern got changed. Who knows which preceded the other.