The 0.5 might be apt, but I don't see it as a former smoker. You can almost make out the B&S springboard draft protruding from the car and in the platform view it's very easy to see both the vertical end sill bolts on the side sill and the molding/beaded facia board at the roof line - both Class 1 boxcar traits not present on the J&S cars. The roof also appears peaked, instead of the sharper curve on the J&S smokers. The door being to the side would simply be to avoid cutting the center end post that supports the ridge beam in the B&S boxcars. I'd say that caboose is a reworked boxcar. While I read somewhere that some of the Class 1 boxcars ended up as sheds, I'd also say not all of them ended up as sheds and probably very few of them. Sloan says cabooses 5-10 were added in 1876, which would mean that after converting the four 1871 J&S cars, they would have only had four cabeese on the road for nearly five years. More plausible would be that DRG converted most of the Class 1 boxcars as needed to cover the period as the Class 2 boxcars were begun in 1872 and the Class 1s were no longer needed. I say as needed since it's clear that at least one Class 1 box survived as such for a while from the Mule Shoe Curve pic of 1877/1878 in Ferrell's 'Early Years' book. So there's another possibility for an interesting model - too bad we can't see the side better to see what became of the side door.