Theres usually a sticker on it to identify. Theres also a sticker on the center of the fan that usually has the manufacturer's logo. Different companies usually use different HSF's or PCB colors/layouts. Post the pic maybe we can help.
I think it's a built by ATi card but if you want to research it more then I did click the link below and then click the link near the bottom of the page that says "how to identify my ATi product". It will help you figure out if it is BBA or built by someone else.