Identify this iron cooking piece for me
It is a stove top griddle.   You set it across two burners (hobs for Brits), and heat it up.

You can use it for any griddled foods:  pancakes, hash browns, grilled sandwiches, hamburgers, steak, and so on. 

The little track around the edge is to capture any juice or fat that run off the surface without making a mess.

You season it like any other cast iron pan.  It is probably easiest to do so in the oven.  You only need to season the cooking surface.

See also:


What&#39;s the best way to season a cast iron skillet?
How to clean and maintain cast iron lids
What oil is best for seasoning a cast-iron skillet