Old wrought iron fences, the bars are usually 1/2 inch diameter round stock spaced 3 1/2 inches apart, old iron bridges, various parts from old farm equipment, if you live in or around an old mining comunity its laying all around the shafts. to check it for one, the cruty rusty stuff will normally have a wood grain pattern visable on the surface, if you put it to a grinder test the sparks will be a steady blood red spark with no burst at the end of the spark, for another test take a chisle and cut 1/3 to 1/2 way through it then bend it in half at the cut, the internal appearance will be dull grey with a woodgrain or rope fiber look, if forging it it needs to be forged at about a welding temp or the fibers will seperate.