Question Why are there two different types of Airport board for MBPro A1278?

[al92]

I ordered a new Airport board for my late 2011 MBPro recently, from ebay. I searched using the Apple identifier - A1278 - and checked that the description said MacBook Pro Unibody, but when it arrived it's not the right part. When I checked the ebay listings again, there appears to be two types of airport board - one with two aerial connections, one with 3. Turns out that I need the one with 3 connections but I'm confused by how there are two different parts for apparently the same machine. Can anyone help?

 

[Lutfij]

Often times the listing on the Ebay can and will be misleading. It's only after hours and hours of research that you end up finding the right part. To add, there's also the added issue of the seller sending out the wrong part. To the latter, you can contact seller and see if a refund can be had or the part exchanged.

As for your question about different parts on the same device, it's highly possible as some revisions might've been introduced or some things were culled to streamline the part/overall experience.