I agree with Hyacinth about the oddball turnlock. Though I think the quality of the bag looks like old Coach, that turnlock makes the entire bag look "off". Plus, the placement of the turnlock looks crooked to me.
I think Whateve is right that the turnlock was replaced. There are a bunch of websites that sell nothing but turnlocks and other purse fittings - many show Coach-type turnlocks and many are similar to the one pictured.
It's a very simple bag, but I certainly couldn't even guess about it's authenticity.