A high percentage of original rifles show the effects of using the "wrong" tool or approach to removal of the breechplug. Many original barrels have the tell tale sign of having been clamped into the checkered jaws of a vise while a frontier repairman used whatever wrench he could fit over the breechplug to turn it out. The tang is usually turned up on the upper sides from fitting the the wrench over the top and then turning the "Village Smithy" loose on it.
I have seen some wrenches that have a V shaped jaw in displays of original gunsmith tools. This V would nicely fit the profile of most breech plug extensions on original rifles and would not have caused damage.
