Field telephone exchange

I'm trying to find details on wiring and repair of a 10 line exchange so we can use our model F phones in real situations. We are also interested in obtaining such a unit but if the price etc. is too high I will construct one from pictures etc. any help would be appreciated

Our new exchange is up and running well and we are now getting much info on this topic. We've acquired the operating instruction manual and details on the earth spike. I've got the steel and one is now being manufactured to fit to the new carrying strap kindly provided by Russell. We've also been given the correct earthing braid to attach exchange to earth spike and discovered why most of the labels on the indicator flaps are missing - they were "Radioactive"!! We do need the correct rear lid as the night buzzer is located within it. If we can't locate one we'll have tot try making it.