NBR 4 Plank Wagon with the illiterate makings used during the mid to late 19th century.
This asset has an optional tarpaulin, which van be selected via the 'Sub meshes' section of the 'Options' screen in the 'Properties' window available in Surveyor.
Thanks to PaulHobbs and Trainboi1 for their mesh library elements, many of which have been used in the model.