Isn't it entirely possible that the original owner ordered the rib on his gun to be concave and un-matted? We all know Lefever would have done so when a gun was special ordered.
I suppose anything is possible within reason. But this theory is highly unlikely for a number of reasons. First, this gun has been sleeved, and the new tubes including their screw-in chokes are a non-standard 30 1/4" long. Also, the barrels were sleeved for a reason, which could include being pitted, ruptured, cut, or other damage that rendered the original ribs unusable. Another factor is that Dan Lefever was quite proud of his rib matting machine... enough so that he utilized the same ribs on the guns built by the three successor companies he started after being forced out of Lefever Arms. Co. by the Durstons. Of course, he may have already been gone by the time this E grade was built.
If we had seen other Lefever guns in this range with this style rib, it might be plausible. But we don't. One possible way to know would be to check if Briley's has any record of the work.