Thanks. No rust at all On the other side brown green stain. Cant clean it yet. But its golden colour. Thinking more on lines of kerosine cap of old tin can
Welch plugs are generally brass and the brown / green could very well be the rust and coolant build up from the inside of an engine and it could be from a tractor or truck and not a car . Some old stationary engines also had these .
That's interesting you say that Doug. When I was a kid my dads car blew a welch plug on a family outing once in the early 1970's. He was a mechanic by trade, and a very resourceful bloke. He rummaged through his mobile toolbox in the back, and came up with a metal screw top from an old Golden Fleece fuel or oil container. It was almost an exact fit for the hole left in the engine block from the blown plug. He put some adhesive goop around the outside of the screw top lid, and placed it nicely in the hole by pressing it in by hitting a large socket that he had that was the same OD as the screw top. It got us home