The hole is a modification, original new services did not have a hole or a screw there. Would need to look closer but it appears that there are British acceptance marks on the upper left side of the frame. The British purchased close to 60,000 for WWI and most were surplussed later. If those are acceptance marks then it was originally a 455 eley and then the barrel and cylinder replace after it was surplussed. Another indication that the barrel was replaced is that it has the taper near the frame and a true 1916 era gun should have a straight barrel. Without the serial number I cann't tell what type of barrel it should have.
As far as value, taking into account the about, it has no collector value and is only worth what someone will give for a good shooter