AS 976 has different sized roller plate?!

[BrianJW]

I'm working on a AS 976. I needed a new hair spring and had a donor junk movement but it's hair spring was in poor condition.So I sourced a NOS on ebay. But once assembled it would swing but not engage te palet. As you can see in the picture the rollers are 2 different sizes(1.5mm and 1.65mm). It also happens that the donor roller has the smaller size as well. What's also different is the size of the balance staff between them is different. 

So here's my question(s): how do I ensure I get the right one? Is this something that is common in vintage movements? Did I get something wrong?  

[JohnR725]

Then just as a reminder swapping hairsprings can be a challenge because there vibrated to each balance wheel.

In the first link you'll notice the reference to the balance jewel assembly? In other words non-shock protected and shock protected that means two separate balance wheels. Then normally get a picture of the front and the back of the movement any variations and you get more pictures like we have here?

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&AS_976

You probably don't want to look at the next link because? One of the problems with some vintage watches it may have gone through evolution of components. Especially if the Watch was made over a long period of time because it was popular or a popular size or some other factor where it evolved a lot. In this link we get a clue to the problem how many Balance completes for your movement? appears to be 11 different balance completes. Then things get more interesting balance staffs there appear to be 19 of those.

You'll notice at the very top of the page is actually tell you which staff is the most popular so this tells the material houses aware of the fact that people might be having confusions but just because it's the most popular doesn't mean it's the one that you Have.

Then it appears to be you have four different roller assemblies.

I think it might help of you would give us complete picture of the movement front and back.

http://cgi.julesborel.com/cgi-bin/matcgi2?ref=AS_976