How can I identify what year an optical drive is from?

I've been working on macs for about 18 months now, and 1 thing that always frustrates me is replacing the optical drives. I often times can't get a replacement drive to work in a MacBook that I know worked in another MacBook.

I'm told there's a way to identify the optical drive to know exactly what year a1278 or a1286 it will work in, but i'm not sure how to do that.

Does anyone know how to identify that to make it easier to know which optical drives I have in stock will work with which model year MBPs??