WC&PR started out with a few ancient pre-1870s wagons of unknown origins but under the management of Col. Stephens they acquired a significant number of later better quality stock, mostly 3 and 5 plank wagons and one ex-GER covered van. Most of the later WC&PR plank wagons were old MR stock which became surplus when in newer production series they updated the initial designs with several improvements and changes. Peter Strange in his book lists 24 numbered Open plank Wagons (WC&PR #2-12, #14-16, #18-27) and attributes them all as ex-MR stock.  

A large amount of valuable help has been given to me by Compound2632 in untangling the mysteries and fascinating history of these supposed ex-MR wagons and other wagons of the era as reported in the following pages. Without his assistance much of this would not have been possible for me as a rank beginner.

The first issue addressed was wagons #14 and #19, reported by Strange as ex-MR 7' wheel base 3 plank wagons and with a photo supplied. The considered view is these ware ancient and do not correspond to any known MR wagon. They remain a mystery and probably date back before records of production were kept. 

Moving on the the ex-MR 3 plank wagons this shows the target, MR D305; Drg 213 from 1887

NRM DY 2490, released under the Creative Commons Attribution-NonCommercial-ShareAlike (CC BY-NC-SA 3.0) licence by the National Railway Museum

The Slaters kit (Drg 1143) for the MR wagon captures most of these changes and so needs backdating to become a Drg 213. Fortunately for me these were easy modifications:

The Buffer Head-stocks of Dia 213 were extended and sloping, effectively incorporating the door stop blocks as "built in"

8A grease axle-boxes vs a later 10A model

Brakes / brake lever only on one side

A re-positioned number-plate

The first two were easy; 1) some 0.75mm Plasticard glued to the existing Head-stocks and shaped once set; 2) a few careful snips to reshape the axle-boxes (fortunate I didn't need to go the other way!)

The braking system was easy as the majority is added during the kit build, the number-plate I assumed was either removed or painted over at WC&PR so I did the latter.  This photo before final finishing