As John says, a 'Factory Undocumented Case' is new one on me as well.
It looks to be a very well adapted 'Brady' case with what appears to be a genuine 'Webley' case label. The only Webley oil cans I know off that have an off centre spout, do not have a valve spout.
The rifle doesn't appear to be anything special and the barrels can't be seen, so their condition is unknown.
The .25 barrel having a different number may slightly affect the price, but a nice three barrelled set will always attract a certain amount of interest, so who knows, but it will be interesting to see the hammer price.