I believe the grain comes from a forged (as opposed to cast) iron process. That could make it much older; but not necessarily. Farmers forged what they needed right up into the early 20th century.
As to what it is? Hinge pin or alignment pin of some type is a good possibility.
Thanks for all the replys!
It was found in California gold/copper mining area. Next to a water flume built by the Chinese around 1920's
I'm actually a tractor/forklift mechanic so I thought about it being a three point pin but looks too old for three point.
Safe bet then its some sort of pin.
And now I know!!
Ill mark "solved" tomorrow some time.