Wagon Lighting /Pooley wagons

[Guy Harding]

I am building Metropolitan Railway Pooley wagon as used by the weighbridge companys engineers to travel round the system and calibrate the weighbridges at stations. They were used on many different railways but usually as conversions of other wagons. This wagon had workshop facilities including a forge. On the roof are two what can best be described as thimbles. They are about 1 inch diameter in our scale and have a series of 1/8 holes around them in three rows. Does anybody know more about them? I presume that they were lighting covers /ventilators and that gas lamps would be hung inside them?

Does anyone have any more information about these? drawings etc. Alos if anyone knows any more about Pooley wagons in general especially the internal layout then all information would be gratefully received.

Thanks

Guy