JimG
Western Thunderer
We can be certain the van in the photo wasn't the CR van built in 1906 as the photo dates from the 1880s.
It might still be a Caledonian or North British van. The Caledonian Diag 1 meat van was produced in 1888 and had smooth, vertical panelled sides with a higher, peaked arc roof. Looking closely at the van in the picture, you can almost see the vertical panelling when trying to rule out wishful thinking. There should be trumpet shaped ventilators on the roof and long thin ventilator grills on the sides just below the roof line, but I cant see enough definition to see if they are there on that van. The Caledonian and North British rolling stock designs had a good few similarities at the time since Dugald Drummond had walked down the road from Cowlairs to St.Rollox in 1882 taking a lot of his designs with him, so there might be a very similar NB design but I don't have a lot of information on NB stock to check.
Jim.