What is this a picture of?
Is the photo in the correct orientation (I assume it is, as it seems to be weathered / rusted more on "top", but just wanted to confirm).
Some photos post sideways here.
Can't help yet with age or purpose.
It looks like barb-wire to me. I recall seeing something somewhere that you could estimate the age of barb-wire by determining the manner of construction (type of barb, twist rate, intervals between barbs, etc...), so maybe that approach could yield some clues.