Why do these old Ridley Heliums (I think 2008) have different seat-stays?

[User Name]

I recently bought the one in the top pic, with the curved seat-stays, but my friend has one exactly like the one in the bottom photo, with straight seat-stays, which are narrow from side on, but quite broad when looking from the rear.

My head-tube is also roughly 5mm bigger, even though they're the same size otherwise.
His also has black rear dropouts, which may or may not be carbon.

So, are they different models? Different years? Why are they different? Is the bottom one a lighter model?
There are no different decals that might indicate such.
I can't find any serial number information to help me.
Thanks

[mr_tim]

Different rear drop out from what I can see.

I have an '09 excaliber which doesnt have that metal rear drop out but I know '08 noah's have it.

I think you've got the earlier year before they did away with the metal formed drop out

[bikerjulio]

I know nothing really about these, but Google would indicate that the carbon dropout version is 2008 and the other is earlier.

http://www.cyclingweekly.co.uk/news/product-news/first-ride-ridley-helium-97168

[User Name]

Thanks for the replies. I wasn't sure I'd get any.
That's interesting. So, it looks like mine is a 2007.