Hi Gary
Did the wagon carry coal for that particular wagons owner all of the time?
Most of the time. They may have been loaded with coal for another agent/merchant to pay their way to their final destination.
Was the wagon leased from the owner to other wagon owners?
Some times there seamed to be 3 ways of paying for the wagon Buy out right, Hire Purchase , or Hire. The first option usually transaction between builder and user. The second 2 options could be with either the builder or a hiring/finance company
Who was responsible for the maintenance of the wagons?
Maintenance was the responsibility of the owner/hiring agent.
Did these wagons stray far from the geographical area displayed on the side?
Yes, location of the wagon would be dependant on the customer preference for the coal supply and that applies to both individual merchants, agents, factors or collieries
Are there any parallels with regards to owners of today's modern wagon fleets like Naco etc?
I couldn't say not knowing anything about modern PO wagons
In addition most PO wagons were pooled between 1917-19 and 1939-47
Marc