"Back work" and "back work and bar" locks need less metal to be machined out of the action , one of the reasons they were used in heavy calibre rifles . Side lock O/Us used them as there was no space for conventional bar lock , guns like the Holland Dominion used them so to get a slimmer rounder body . Many Continental makers used them because that's the way they made guns .
Never seem a back work and bar lock with a fake pin so as far as I am concerned if it hasn't got a pin on the bar its a back work.
