G.T. Parker & Sons were a private merchant company based in Boston (Lincolnshire), using wooden 7-plank open wagons like this from the late 19th century into the 1940s.
These wagons carried coal, building materials, produce, and other general freight. The 7-plank design allowed for a heavier cargo load compared to 5 or 3 plank variants.
This TT:120 7-plank wagon, in a black livery finished with white lettering and red drop shadow; 'G.T.Parker & Sons', is carrying the number '19'. 
Pairing with a small steam locomotive such as a Jinty or Peckett will create an authentic scene for this wagons’ time period.