The Highland Railway's Diagram 12 fish truck was the earliest of three types of open wagon for transporting fish in passenger-rated trains. There seems to be some uncertainty as to the exact livery - some speculate it was painted in goods red, others in passenger green - of course it's possible that they appeared in both if the type was moved from the wagon register to the NPCS register (or whatever it was that the Highland used to differentiate stock).     I was impressed with Pete Armstro