Waht is the body made of? Is it diecast or detailed plastic. P&D made very nice bodies in plastic with great details all added separately. Diecast could be All Nation or one of it's predecssors, General Models or Adams castings.
If the body is fabricated brass it could have been salvaged from dead import unit.
Also what do the trucks look like up close. P&D does very nice super detail brass assembled somewhat like the prototype. All Nation and General Models are diecast.